Try to write concise, specific tips. Please avoid duplicates. I am arbitrarily ranking the tips from most important to least.
General
- Scouting is cruicial:
a) It is essential that your scounting worker is kept alive as long as possible. If something seems wrong, send one or two more workers to popular proxy positions.
b) In the mid-game, if you're not getting attacked, scout with a worker or two (Zerglings if Zerg) and use Ovies/Obs/Scanners to see if they're going Hive/Carrier/BC/Arbiter Tech, Mass Expo, or Massing to 200/200. Better safe than sorry.
c) Always leave a worker outside their choke. Later, leave one at each potential expo. Zerg should put Zerglings there, which is even more effective for killing workers. - Forget about APM. If you focus on how to play then your apm will go up; Many people actually detract from their game because they are ostensibly 'raising their apm' when they should just learn how to win.
- Play all races to get a feel for timing,even if you play only one race, it helps tremendously. You don't necessarily need to play every matchup, but a few games of each inverse helps a ton.
- To unload a dropship while it moves, click unload (or U) and click on the dropship.
- Don't get cocky if you have the advantage; Play for the best chance to win, not the fastest way to win.
- If their gas is free early game in ZvZ, TvP, PvT, PvP, or TvT, steal it. This can really mess up whatever strategy they had in mind. This can also to other matchups if it looks like they are not going for a fast expansion build.
- Spend one game practicing where to put all your buildings so your units don't get stuck and it's easy to macro.
- Don't be afraid to queue up 2-3 units at a time. If you were a perfect player with 350 apm you wouldn't need to do this, but you aren't, so it is necessary sometimes. As long as you have enough macro facilities this isn't so bad.
- Don't be afraid to make extra production facilities if you need them, despite how many you see better players make. If you have perfect macro you wouldn't need them, but you will improve your macro if you can support extra production.
- Ensure that you have Pylons, Supply Depots and Overlords well placed in your base to prevent in-base proxies due to the fog of war. If possible, have vision of your natural minerals to allow workers to run more easily from drops, Mutalisks, and to block units trying to break your ramp.
- Once you have a central production area with many facilities give it a a Shift+F2 and use that to macro.
- Hide your scouting worker in the opponent's base when scouting. Sometimes they won't find it and you can scout their tech more easily. If it is found, just scout normally.
- Use Shift+action to queue up actions. Very useful for scouting with waypoints or telling Probes/SCVs to return to mining once the finish contructing/warping in a building.
- Control+LClick selects similar units. Shift+LClick removes/adds a unit to the current selection. Alt+LClick selects the last selection group that unit was a part of.
Protoss
- Place Pylons or Observers along obvious drop paths to scout incoming drops.
Terran
- Terran should not care about 2 Cannons; just focus fire as many Probes as possible.
Zerg
- If your expansion is blocked by a worker, group the Drone with an Overlord and place it on hold position. Now the Drone can attack from that spot without moving while you spam B H repeatedly. As soon as the Probe gives you enough space, which is very little, your Drone will turn into a Hatchery.
- When trying to consume Zerglings during a battle, tell them to hold position first so they are easier to target.
- Consume irradiated Defilers and Lurkers. Morph irradiated Hydralisks to Lurkers. Use irradiated Ultralisks to deal splash damage to Marines.
- To kill a worker with Zerglings, first run near the worker allowing it to attack you. This will ensure it doesn't automatically run away when you attack it.
- When fighting Corsairs with Mutalisks and Scourge, engage with Mutalisks first to soak up damage, and then send in Scourge from a different angle to avoid dying to splash damage.
- Burrow lurkers at the top of ramps to make it practically impossible for Marines to get up without Tanks or Irradiate.
- In ZvT use 12 Speedlings to backstab Terran when he moves out for his first attack; in ZvZ use 4-12 Zerglings to backstab Zerg when he moves out with his entire Zergling army. Target the workers.
- 4 Drones are enough to destroy enemy Sunken Colony that has just started morphing; 2 Drones attacking a Creep Colony, and then adding a third when it morphs to a Sunken Colony will destroy it.
- For close positions in ZvZ, sending your ninth Drone to block his natural Hatchery.
- If you are planning on backstabbing a Terran with Zerglings, put your Zergling scout on hold position so he doesn't see you have Zergling Speed when he moves out.
- In ZvZ, Overlords soak up a lot of Mutalisks bounce damage, which will help you win large Mutalisks battles.
- Building an extractor and cancelling it will return your Drone to full health - this is useful against worker harassment.
- Keeping 1-3 Lurkers on hold position behind expansions will allow you to kill all his workers once he transfers them.