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 your workers are running around instead of mining then...
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 then 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 standard 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.
Part 1: Picking a Race
Part 3: Dictionary of SC2 Terms
Part 4: Build Orders
Part 5: What you might not know
Part 6: The advantage