Image via Wikipedia1. Learn to use keyboard shortcuts: I really can't emphasize this point enough. If you're spending time clicking on individual buildings to make units, you're wasting a lot of time that could be spent either microing or macroing up your forces. Quiz: what are the hotkeys for a marine, zergling, zealot, stalker, etc? If you don't know, you should take the time to learn these if you want to advance your game.
2. Hotkey your production buildings and units: Again, if you're spending time during a battle clicking back to your main base to make more units, you're wasting valuable screen time that could be spent microing your units. Personally, I like to put all of the production buildings of a single type on a hotkey and the same types of units on the same hotkey. Let me give an example of how this would work in a game.
Lets say that I'm playing terran and I'm into the middle stages of a game and doing a banshee / viking / marine build. Also, lets say that I have 4 barracks (with 3 reactor cores and one tech lab), 1 factory (with a tech lab) and 4 starports (3 tech labs and 1 reactor core) supporting my build. In this case, I would put all of my barracks on one hotkey (usually 9), my factory on another hotkey (8), and all of my starports on a third hotkey (7). Additionally, I would have each of my troop groups on a different hotkey: in this case, my banshees on one hotkey (1), my vikings on a second hotkey (2), and my marines on a third hotkey (3). If I have some spell casters (say a raven), I would put these on a different hotkey (4). If you do this consistently, the macro and micro parts of the game will both become much, much easier in the long run.
3. Learn to micro your units: Starcraft 2 is all about two things -- building the right units at the right time and micromanaging those units. A lot, probably most, of the players in the bronze and silver leagues consistently forget to do the latter of those two tasks. Microing your units during a fight can literally make the difference between winning and losing the battle. For example, if you're playing terran and you reaper rush and your opponent has too many marines to handle, don't just let your units run into his marines and die. If you run your units around his base for long enough (and keep building new reapers at your main via the hotkeys discussed earlier), you WILL eventually have enough reapers to take out his marines (if he keeps only building marines), especially since reapers are a hard counter to marines. Remember: four marines versus two reapers is a battle you might lose. However, eight reapers versus 12 marines is probably an easy victory for you. Wait until you have the forces to win the battle decisively.
4. Learn unit counters: In Starcraft: Broodwars, you could basically build any unit you wanted in the middle and late game and, if your macro game was good enough, you could probably overrun your opponent, even if they were building counters to your units. For example, in Broodwars, I would sometimes get lazy as protoss and build nothing but dragoons all game long. Even with this dumb strategy, unless my opponent was zerg and building tons of zerglings, I would win a much larger percentage of the time than I deserved to win. However, you can't do this in Starcraft 2. In Starcraft 2, every unit has a counter to it. In other words, even if your opponent has an army twice the size of yours, you can win a battle easily if you have the right counter units. An example of this is a recent game where I played terran and saw that my opponent was building massive amounts of zerglings. I built up a force of about 18 reapers and put them at the choke point for my base. My 18 reapers took out something like 40 zerglings in about 5 seconds when my opponent decided to attack my base. Starcraft 2 has tons of these types of counters that make it impossible to win a game using macro alone against a smart player. Learn what those counters are and use them to your advantage.
5. Learn to scout: Part of successfully using counters in your game is scouting the enemy base. In my opinion, it is very hard to overscout the enemy base -- as long as you're getting good information in exchange for the price. If you can remember to actively scout your opponent's base all game long, you should see your level of play rise dramatically.
