Here's another great guide made by Duban of Starcraft 2 community
I've played the beta and am a pretty good player. If there is one thing I've found to be critical to playing well it is choosing the right race. To do well you shouldn't pick Terran because they are human, Protoss because they are cool and high tech, or zerg because of their monstrous appetite.
Each race has a distinct play-style and/or play-styles unique to their race. Each player has a play-style that best suits their own personal play-style and play level. To do the best you can you need to find the play-style that best suits yourself, and then pick your race accordingly. Here are the races and how they play.
Terran: Terran is an extremely defensive race. The race centers around creating a heavily fortified position in the early game, usually by creating a front door wall with supply depots, barracks, and/or factories. The Terrans than build up a large force unopposed and move out when the time is right. Because Terran strategy is very straightforward and in the process of climbing the tech tree they unlock almost everything Terran is generally considered the "Easy" race.
If the Terrans have a weakness it is that they can only operate as many bases as they can defend at one time. Terrans are usually limited to only 1 or 2 bases. Their units are slow and largely dependant on positioning. They are superior in a chokepoint but weak on open ground.
Zerg: If the Terran race says "This is my base and you can't do anything to stop me from holding it" the typical Zerg response is "Ok, but I get the other 90% of the map". Zerg gets a large number of extremely mobile units. Speed upgraded Zerglings are lightning fast, mutalisks are fast and flexible, Roaches and infesters can travel while burrowed. The Terran fight in a chokepoint, like near their base, and the Zerg fight in the open ground of the center of the map.
The zerg win by out-producing, or out-macroing, their opponent. Good Zerg players usually fall into one of two categories. There are the players who build almost nothing but drones as much as they can, for as long as they can. At any one point they have just enough forces to survive for now, and they build much of their army after they spot the enemy army leaving their base. They build nothing but the best counter for the opponent's forces.
The other strategy revolves around taking an active part in preventing the opponent from being able to macro. These players use their high mobility units to constantly harass their enemy. Often attacking the opponent's workers with mutalisks and other surprises. Instead of bolstering their own economy they build fast units and stop their opponent's. Constant harass, mutalisks, baneling drops, anything to slow the opponent is standard.
If the Zerg have a weakness it is that all of their strategies are highly dependant on the player's skill. A macro heavy zerg needs to know exactly how large an army the opponent could have at any given time, and exactly how much of an army he will need to keep to stop that army. A harass heavy zerg needs unparalleled control over his units to keep them constantly moving and attacking. The zerg is often considered the "hard" race, BUT if you're willing to work with their play-style it can also give great results and be very rewarding at the same time.
Protoss: There is a reason I'm covering Protoss last and that is because the Protoss race is best compared side by side with the other races. The Protoss can play very aggressively, using warp in and a large number of gateways to quickly drop a strong force on the enemies doorstep. A front door closed by gateways and a zealot or two at the entrance can be difficult to break.
The Protoss can put up a strong defense compared to the zerg, but not nearly as tough as the Terrans. The Protoss forces are more mobile than the Terrans but can expect to be outmaneuvered by the Zerg. The Protoss are strong against the zerg in a tight chokepoint, but should fight the Terrans on open ground. They can expand to a new base early, or live off of 1 base for some time.
The Protoss doesn't really have a definite weakness, but it doesn't specialize either. Its better than zerg at things zerg is bad at and better than Terran at things Terran is bad at. Its a very well rounded race in general. Protoss are generally considered to be the moderately difficult race as the race doesn't require quite as much micro and knowledge as the Zerg, but he still needs to know how to be effective against an opponent using a given strategy.
Basic Rules to Live By
There are exceptions to almost every rule, but I'll be compiling a list of basic rules of thumb that are generally a good idea to follow. This is a list of tips and tricks that will help keep you competitive in SC2.
1) Keep building workers out of all of your nexii, hatcheries, and command centers. Never stop. If you've maxed out your workers in one base and you're workers are running around instead of mining than...
2) Expand to a new location and send workers to the new location. Build another nexus, hatchery, or command center before your first base has run out of resources. The best thing you can do is to expand as soon as you can, without leaving yourself vulnerable to being overrun.
3) Don't leave resources such as gas or minerals lying around. If you have resources sitting around doing nothing than those resources are useless to you. If you don't spend them you might as well not have them. Always use every mineral and gas you have. If you have 5000 minerals lying around than build a bunch of gateways, hatcheries, or Barracks and start pumping out cheap units in large numbers. Your resources aren't doing you any good if you don't use them. If you must, expand and start collecting more gas .
4) Don't focus too much on static defense. A few photon cannons, spine crawlers, or bunkers can help you hold off your opponent in the early game while you build up a more comprehensive army, but don't expect them to hold off forever. Attack/armor upgrades only affect your units, not your buildings. Eventually your defenses will become weak and crumble to upgraded siege units such as brood lords, siege tanks, or colossi. Even worse, your opponent might just go around them and destroy your unprotected base.
5) Learn to balance economy and your army. From time to time in your game think "ok, can I afford the minerals to build another expansion?" and "Do i have the forces to defend that expansion?". Knowing when to expand and when to focus on your army take experience, but in order to get better at it you must first try.
6) Don't focus only on winning with cheese. Sure you might beat some newbs, and it might look like easy wins for a while but it won't last. Eventually you'll fight better players and you'll find your cheese has stopped working. You'll be forced to use non-cheese strategies only to find out you don't have the slightest idea how to beat a good player without cheesing. Cheese can be a fun and amusing change of pace, but it shouldn't be the only thing you do.
7) Playing with the mindset that something is "cheap" is a good way to lose. Don't whine every time you lose in a way that you didn't expect. Instead watch the replay, think about what happened, think about what you could have done to stop it, and if you still can't figure it out come to the forums and ask what you could have done differently. The game isn't perfectly balanced but in most cases it is a better idea to learn how to stop strategies instead of whining about how you lost to them
8) Build only as much supply as you need and build it as you need it. Don't waste 2000 minerals on overlords, pylons, and supply depots that you don't need. Remember, that's 2000 minerals you could be putting toward troops or on a nexus/hatch/CC. Build your supply units just before you need them. An overlord at 9 supply, 15 supply , and 25 supply is all you really need. There's no need to build 4 supply depots before your second rax.
Dictionary of SC2 Terminologies
Seeing as there will be a large number of players new to starcraft and even RTS games in general I've compiled a dictionary of frequently used SC and SC2 terms.
SC2 dictionary standard:
Micro- Unit control in an individual battle or harass. A player's ability to get the most out of the units he/she owns through superior control.
Macro-The combination of a player's ability to gather resources and produce units. The player's ability to produce a large army.
Cheese- An all in strategy that is highly unorthodox and usually involves taking an opponent by surprise.
Tech or Teching- Concentrating on advancing up to better buildings and units. To tech or the act of teching involves racing to or attempting to get the most advanced units in the game.
Rush- Attempt to amass a large army very quickly. In a rush you sacrifice your economy and tech in order to overrun your opponents early on while he/she is unprepared.
Harass- As the name implies. Rather than trying to overrun your opponent completely you attempt to weaken him with smaller attacks. workers are the standard target although occasionally you'll see a player take out lone units or buildings.
Pro- Professional, people who actually make their living in SC2 tournaments. Seriously don't think you're "pro" just because you get the basics of the game.
Build, Build Order, or BO- A set order of constructing units and buildings. Often expressed in terms of supply count. A 9 pool for example is a spawning pool built at 9 supply/workers.
Proxy- Buildings that are built near your opponent instead of in your own base. It usually means you're attempting to build your units closer to your enemy so you can attack without having to cross the map. See Cheese.
Main- Your first base, your starting location
Natural- The mineral/gas location directly outside of your Main.
Third, fourth, etc- additional base locations.
AA- Anti-Air. Standard RTS term.
Zerg related:
Ling- zergling, SC1 term. Avoid if possible to avoid confusion with baneling
Speedling- speed upgraded zerglings. Speed upgrade is critical.
Crackling- zergling with speed upgrade AND the attack upgrade at pool. SC1 term.
Muta- mutalisk
Muta ling- A strong combination of mutalisks and zerglings
Muta ling baneling- muta ling with small numbers of banelings.
Ultra- Ultralisk.
Hydra- Hydralisk
Pool- spawning pool
Hatch- hatchery
Terran related:
MMM or 3M-Marine, Marauder, Medivac.
Bio- See MMM
Mech- builds consisting primarily of Factory units. Occasionally with viking and/or marauder support.
Stim- stimpack
Rax- barracks
CC- Command Center
Protoss related:
Lot- zealot, used rarely.
Blink Stalkers- Stalkers with blink.
Chargelots- Zealots with charge
VR- Void Ray
DT and HT- Dark Templar and High Templar, respectively.
FF- Force Field
Hallu- Hallucination. SC1 term, relic term and rarely used.
MS- Mothership
Build Order (BO)
First off, what is a build order(BO)?
Literally, a build order is a set of instructions on the order and timing of buildings and units you construct. The timings are usually timed by your supply count. At a set time you should have X supply, and when you have X supply you know its time to build a given building or unit. Its a set of orders and instructions.
Figuratively, a build order is the refinement of an idea. At first you know what you want to do, but you don't know exactly how to work it into your strategy without sacrificing too much else. You don't know when you'll have the minerals/gas to spare, when you need to start mining gas to time everything perfectly, and you don't want to go into it without a plan. So you create a build order
Example: Basic Zerg Fast Expand BO
9- Overlord(OL)
14- Spawning Pool
15- Hatchery
15- Extractor
15- OL
This is a very basic build order for a fast expand. It has been refined and worked until it covers everything you need. It has the 14 spawning pool to defend an early attack but still gets a fast expansion, followed by the gas you need, and finished with an overlord so you can continue to build when it is all complete.
How do I go about creating a build order?
Creating a good build order is a critical skill to master, but it can be difficult if you don't have the slightest idea where to begin. First you start off with a basic idea of what you want to do. Lets say you want to try a powerful mid-early marine rush with an extremely fast stimpack and marine shield upgrade.
So you lay out a basic plan. You want to get some fast barracks but you'll need early tech labs so you can train stimpack and marine shield, thus you need early gas too so you'll go refinery before barracks. Soon after that you want two more barracks with reactors to mass produce marines. You need a basic, reliable, but not too hard opponent to play against so you pick a medium-low computer to try it out on. You try your strategy without a set build order in mind.
Next you go back and watch the replay and take note of at what supply you built everything. You write that down and see what the weak points of the build were and refine the original build. Lets say you note that the generator on the fourth rax was pointless, it took too much time to build and you were better off just pumping from the rax so you could get the attack out earlier. You also note that you have plenty of resources later on but if you call a supply drop instead of a mule you'll have the resources early on to build your third barracks sooner, even if you're 170 min behind in the end. You need the barracks now and the resources later are not important.
Ok so finally you try the refined build against another computer and it all works out very well, you're pleased with the results. You've got a working build, but you need just 1 or 2 minor tweaks before you pit it against another player. Lets say you realize that stimpack takes 30 second longer to complete than the marine shield upgrade, so you start training stimpack before the shield instead of after. This way they both complete at the same time and you can move out sooner.
Now you're ready to try your refined build order against another player. It has to come eventually, so GO FOR IT!
What you might not know
Alright I've written a new part. We now have part 5, a list of information I've found that you might not know, even if you've been playing for a while.
1) Each worker you put on a mineral patch will mine roughly 40 minerals per minute. A second worker on the same mineral patch will also mine 40 minerals per minute. A third worker will only give you 20 minerals per minute. A fourth worker will mine very little. This means 16 miners on the minerals of a base will work at full, while miners 17-24 will work at half capacity, and 25+ is just not worth it.
2) The extractor trick, where you build your overlord at 10 supply and then build an extractor for an 11th drone is inferior to just building your overlord at 9. Multiple tests have shown 9 OL to be about 10-15 minerals better than the 10 extractor trick. The extractor trick can be used, but only if you plan on building your spawning pool at 11 or 12 supply.
3) Unlike in SC1 there is no reason to split your workers individually when the game starts in the old style of SC1. Its been shown that there is no distinguishable difference. However splitting your workers into two groups of 3 and telling each group to move to a different side of the mineral patch will give you 10-15 more minerals. While it takes practice and skill to pull this off successfully it is worth it if you can.
4) A common misconception is that banelings are weak against zealots. While it does take a considerable number of banelings to kill a single zealot if you micro them into a group of zealots the entire Speedling Vs Zealot dynamic changes. While you may only kill one or two zealots you will cut the Zealots' life in half.
The zealot's main advantage in this battle is that the zealots can take down a zergling or two before they die, even when surrounded. Cut the zealot's life in half, and their effectiveness plummets to zero very quickly. Baneling the zealots and attack quickly, before their shields can regenerate. Just make sure to move the banelings normally, not attack move, so the banelings are packed tightly with the zealots just before blowing them up.
5) The mule ability at the orbital command mines 270 ore in the time it takes to regenerate 50 energy. This is about as effective as 6 SCVs. The supply drop gives you 1 supply depot worth of supply or a value of 100 minerals. In very specialized builds the instant 100 minerals can help you build a barracks or factory if you plan to have plenty of minerals later, but need the production building or CC now. In most cases the mule should be used, and used extensively.
6) The ghost's snipe ability costs only 25 energy, comes on a cloaked unit, and deals 45 damage to biological units. SCVs and drones have 45 HP or less and even one ghost can hold enough energy for quite a few snipe attacks. The attacks can also be made in quick succession *hint hint*. Oh, and mass snipe is also quite a heavy damage dealer against biological units like zerg. 45 damage per shot with a short cooldown rate. Just don't make your entire army revolve around ghosts.
7) A lot of good players have figured this out, but queens actually make decent early AA. A lot of higher level players will make an extra queen, stick it between the natural and main, and use it to fight off any fast early void ray or banshee rush. Its even better if you use transfuse to boost the hp of the queens. It can easily save you until you can make it to hydra/mutalisk and get some proper AA.
I've played the beta and am a pretty good player. If there is one thing I've found to be critical to playing well it is choosing the right race. To do well you shouldn't pick Terran because they are human, Protoss because they are cool and high tech, or zerg because of their monstrous appetite.
Each race has a distinct play-style and/or play-styles unique to their race. Each player has a play-style that best suits their own personal play-style and play level. To do the best you can you need to find the play-style that best suits yourself, and then pick your race accordingly. Here are the races and how they play.
Terran: Terran is an extremely defensive race. The race centers around creating a heavily fortified position in the early game, usually by creating a front door wall with supply depots, barracks, and/or factories. The Terrans than build up a large force unopposed and move out when the time is right. Because Terran strategy is very straightforward and in the process of climbing the tech tree they unlock almost everything Terran is generally considered the "Easy" race.
If the Terrans have a weakness it is that they can only operate as many bases as they can defend at one time. Terrans are usually limited to only 1 or 2 bases. Their units are slow and largely dependant on positioning. They are superior in a chokepoint but weak on open ground.
Zerg: If the Terran race says "This is my base and you can't do anything to stop me from holding it" the typical Zerg response is "Ok, but I get the other 90% of the map". Zerg gets a large number of extremely mobile units. Speed upgraded Zerglings are lightning fast, mutalisks are fast and flexible, Roaches and infesters can travel while burrowed. The Terran fight in a chokepoint, like near their base, and the Zerg fight in the open ground of the center of the map.
The zerg win by out-producing, or out-macroing, their opponent. Good Zerg players usually fall into one of two categories. There are the players who build almost nothing but drones as much as they can, for as long as they can. At any one point they have just enough forces to survive for now, and they build much of their army after they spot the enemy army leaving their base. They build nothing but the best counter for the opponent's forces.
The other strategy revolves around taking an active part in preventing the opponent from being able to macro. These players use their high mobility units to constantly harass their enemy. Often attacking the opponent's workers with mutalisks and other surprises. Instead of bolstering their own economy they build fast units and stop their opponent's. Constant harass, mutalisks, baneling drops, anything to slow the opponent is standard.
If the Zerg have a weakness it is that all of their strategies are highly dependant on the player's skill. A macro heavy zerg needs to know exactly how large an army the opponent could have at any given time, and exactly how much of an army he will need to keep to stop that army. A harass heavy zerg needs unparalleled control over his units to keep them constantly moving and attacking. The zerg is often considered the "hard" race, BUT if you're willing to work with their play-style it can also give great results and be very rewarding at the same time.
Protoss: There is a reason I'm covering Protoss last and that is because the Protoss race is best compared side by side with the other races. The Protoss can play very aggressively, using warp in and a large number of gateways to quickly drop a strong force on the enemies doorstep. A front door closed by gateways and a zealot or two at the entrance can be difficult to break.
The Protoss can put up a strong defense compared to the zerg, but not nearly as tough as the Terrans. The Protoss forces are more mobile than the Terrans but can expect to be outmaneuvered by the Zerg. The Protoss are strong against the zerg in a tight chokepoint, but should fight the Terrans on open ground. They can expand to a new base early, or live off of 1 base for some time.
The Protoss doesn't really have a definite weakness, but it doesn't specialize either. Its better than zerg at things zerg is bad at and better than Terran at things Terran is bad at. Its a very well rounded race in general. Protoss are generally considered to be the moderately difficult race as the race doesn't require quite as much micro and knowledge as the Zerg, but he still needs to know how to be effective against an opponent using a given strategy.
Basic Rules to Live By
There are exceptions to almost every rule, but I'll be compiling a list of basic rules of thumb that are generally a good idea to follow. This is a list of tips and tricks that will help keep you competitive in SC2.
1) Keep building workers out of all of your nexii, hatcheries, and command centers. Never stop. If you've maxed out your workers in one base and you're workers are running around instead of mining than...
2) Expand to a new location and send workers to the new location. Build another nexus, hatchery, or command center before your first base has run out of resources. The best thing you can do is to expand as soon as you can, without leaving yourself vulnerable to being overrun.
3) Don't leave resources such as gas or minerals lying around. If you have resources sitting around doing nothing than those resources are useless to you. If you don't spend them you might as well not have them. Always use every mineral and gas you have. If you have 5000 minerals lying around than build a bunch of gateways, hatcheries, or Barracks and start pumping out cheap units in large numbers. Your resources aren't doing you any good if you don't use them. If you must, expand and start collecting more gas .
4) Don't focus too much on static defense. A few photon cannons, spine crawlers, or bunkers can help you hold off your opponent in the early game while you build up a more comprehensive army, but don't expect them to hold off forever. Attack/armor upgrades only affect your units, not your buildings. Eventually your defenses will become weak and crumble to upgraded siege units such as brood lords, siege tanks, or colossi. Even worse, your opponent might just go around them and destroy your unprotected base.
5) Learn to balance economy and your army. From time to time in your game think "ok, can I afford the minerals to build another expansion?" and "Do i have the forces to defend that expansion?". Knowing when to expand and when to focus on your army take experience, but in order to get better at it you must first try.
6) Don't focus only on winning with cheese. Sure you might beat some newbs, and it might look like easy wins for a while but it won't last. Eventually you'll fight better players and you'll find your cheese has stopped working. You'll be forced to use non-cheese strategies only to find out you don't have the slightest idea how to beat a good player without cheesing. Cheese can be a fun and amusing change of pace, but it shouldn't be the only thing you do.
7) Playing with the mindset that something is "cheap" is a good way to lose. Don't whine every time you lose in a way that you didn't expect. Instead watch the replay, think about what happened, think about what you could have done to stop it, and if you still can't figure it out come to the forums and ask what you could have done differently. The game isn't perfectly balanced but in most cases it is a better idea to learn how to stop strategies instead of whining about how you lost to them
8) Build only as much supply as you need and build it as you need it. Don't waste 2000 minerals on overlords, pylons, and supply depots that you don't need. Remember, that's 2000 minerals you could be putting toward troops or on a nexus/hatch/CC. Build your supply units just before you need them. An overlord at 9 supply, 15 supply , and 25 supply is all you really need. There's no need to build 4 supply depots before your second rax.
Dictionary of SC2 Terminologies
Seeing as there will be a large number of players new to starcraft and even RTS games in general I've compiled a dictionary of frequently used SC and SC2 terms.
SC2 dictionary standard:
Micro- Unit control in an individual battle or harass. A player's ability to get the most out of the units he/she owns through superior control.
Macro-The combination of a player's ability to gather resources and produce units. The player's ability to produce a large army.
Cheese- An all in strategy that is highly unorthodox and usually involves taking an opponent by surprise.
Tech or Teching- Concentrating on advancing up to better buildings and units. To tech or the act of teching involves racing to or attempting to get the most advanced units in the game.
Rush- Attempt to amass a large army very quickly. In a rush you sacrifice your economy and tech in order to overrun your opponents early on while he/she is unprepared.
Harass- As the name implies. Rather than trying to overrun your opponent completely you attempt to weaken him with smaller attacks. workers are the standard target although occasionally you'll see a player take out lone units or buildings.
Pro- Professional, people who actually make their living in SC2 tournaments. Seriously don't think you're "pro" just because you get the basics of the game.
Build, Build Order, or BO- A set order of constructing units and buildings. Often expressed in terms of supply count. A 9 pool for example is a spawning pool built at 9 supply/workers.
Proxy- Buildings that are built near your opponent instead of in your own base. It usually means you're attempting to build your units closer to your enemy so you can attack without having to cross the map. See Cheese.
Main- Your first base, your starting location
Natural- The mineral/gas location directly outside of your Main.
Third, fourth, etc- additional base locations.
AA- Anti-Air. Standard RTS term.
Zerg related:
Ling- zergling, SC1 term. Avoid if possible to avoid confusion with baneling
Speedling- speed upgraded zerglings. Speed upgrade is critical.
Crackling- zergling with speed upgrade AND the attack upgrade at pool. SC1 term.
Muta- mutalisk
Muta ling- A strong combination of mutalisks and zerglings
Muta ling baneling- muta ling with small numbers of banelings.
Ultra- Ultralisk.
Hydra- Hydralisk
Pool- spawning pool
Hatch- hatchery
Terran related:
MMM or 3M-Marine, Marauder, Medivac.
Bio- See MMM
Mech- builds consisting primarily of Factory units. Occasionally with viking and/or marauder support.
Stim- stimpack
Rax- barracks
CC- Command Center
Protoss related:
Lot- zealot, used rarely.
Blink Stalkers- Stalkers with blink.
Chargelots- Zealots with charge
VR- Void Ray
DT and HT- Dark Templar and High Templar, respectively.
FF- Force Field
Hallu- Hallucination. SC1 term, relic term and rarely used.
MS- Mothership
Build Order (BO)
First off, what is a build order(BO)?
Literally, a build order is a set of instructions on the order and timing of buildings and units you construct. The timings are usually timed by your supply count. At a set time you should have X supply, and when you have X supply you know its time to build a given building or unit. Its a set of orders and instructions.
Figuratively, a build order is the refinement of an idea. At first you know what you want to do, but you don't know exactly how to work it into your strategy without sacrificing too much else. You don't know when you'll have the minerals/gas to spare, when you need to start mining gas to time everything perfectly, and you don't want to go into it without a plan. So you create a build order
Example: Basic Zerg Fast Expand BO
9- Overlord(OL)
14- Spawning Pool
15- Hatchery
15- Extractor
15- OL
This is a very basic build order for a fast expand. It has been refined and worked until it covers everything you need. It has the 14 spawning pool to defend an early attack but still gets a fast expansion, followed by the gas you need, and finished with an overlord so you can continue to build when it is all complete.
How do I go about creating a build order?
Creating a good build order is a critical skill to master, but it can be difficult if you don't have the slightest idea where to begin. First you start off with a basic idea of what you want to do. Lets say you want to try a powerful mid-early marine rush with an extremely fast stimpack and marine shield upgrade.
So you lay out a basic plan. You want to get some fast barracks but you'll need early tech labs so you can train stimpack and marine shield, thus you need early gas too so you'll go refinery before barracks. Soon after that you want two more barracks with reactors to mass produce marines. You need a basic, reliable, but not too hard opponent to play against so you pick a medium-low computer to try it out on. You try your strategy without a set build order in mind.
Next you go back and watch the replay and take note of at what supply you built everything. You write that down and see what the weak points of the build were and refine the original build. Lets say you note that the generator on the fourth rax was pointless, it took too much time to build and you were better off just pumping from the rax so you could get the attack out earlier. You also note that you have plenty of resources later on but if you call a supply drop instead of a mule you'll have the resources early on to build your third barracks sooner, even if you're 170 min behind in the end. You need the barracks now and the resources later are not important.
Ok so finally you try the refined build against another computer and it all works out very well, you're pleased with the results. You've got a working build, but you need just 1 or 2 minor tweaks before you pit it against another player. Lets say you realize that stimpack takes 30 second longer to complete than the marine shield upgrade, so you start training stimpack before the shield instead of after. This way they both complete at the same time and you can move out sooner.
Now you're ready to try your refined build order against another player. It has to come eventually, so GO FOR IT!
What you might not know
Alright I've written a new part. We now have part 5, a list of information I've found that you might not know, even if you've been playing for a while.
1) Each worker you put on a mineral patch will mine roughly 40 minerals per minute. A second worker on the same mineral patch will also mine 40 minerals per minute. A third worker will only give you 20 minerals per minute. A fourth worker will mine very little. This means 16 miners on the minerals of a base will work at full, while miners 17-24 will work at half capacity, and 25+ is just not worth it.
2) The extractor trick, where you build your overlord at 10 supply and then build an extractor for an 11th drone is inferior to just building your overlord at 9. Multiple tests have shown 9 OL to be about 10-15 minerals better than the 10 extractor trick. The extractor trick can be used, but only if you plan on building your spawning pool at 11 or 12 supply.
3) Unlike in SC1 there is no reason to split your workers individually when the game starts in the old style of SC1. Its been shown that there is no distinguishable difference. However splitting your workers into two groups of 3 and telling each group to move to a different side of the mineral patch will give you 10-15 more minerals. While it takes practice and skill to pull this off successfully it is worth it if you can.
4) A common misconception is that banelings are weak against zealots. While it does take a considerable number of banelings to kill a single zealot if you micro them into a group of zealots the entire Speedling Vs Zealot dynamic changes. While you may only kill one or two zealots you will cut the Zealots' life in half.
The zealot's main advantage in this battle is that the zealots can take down a zergling or two before they die, even when surrounded. Cut the zealot's life in half, and their effectiveness plummets to zero very quickly. Baneling the zealots and attack quickly, before their shields can regenerate. Just make sure to move the banelings normally, not attack move, so the banelings are packed tightly with the zealots just before blowing them up.
5) The mule ability at the orbital command mines 270 ore in the time it takes to regenerate 50 energy. This is about as effective as 6 SCVs. The supply drop gives you 1 supply depot worth of supply or a value of 100 minerals. In very specialized builds the instant 100 minerals can help you build a barracks or factory if you plan to have plenty of minerals later, but need the production building or CC now. In most cases the mule should be used, and used extensively.
6) The ghost's snipe ability costs only 25 energy, comes on a cloaked unit, and deals 45 damage to biological units. SCVs and drones have 45 HP or less and even one ghost can hold enough energy for quite a few snipe attacks. The attacks can also be made in quick succession *hint hint*. Oh, and mass snipe is also quite a heavy damage dealer against biological units like zerg. 45 damage per shot with a short cooldown rate. Just don't make your entire army revolve around ghosts.
7) A lot of good players have figured this out, but queens actually make decent early AA. A lot of higher level players will make an extra queen, stick it between the natural and main, and use it to fight off any fast early void ray or banshee rush. Its even better if you use transfuse to boost the hp of the queens. It can easily save you until you can make it to hydra/mutalisk and get some proper AA.