I'm going to list out the best ways to get better at Starcraft 2. These are the methods that I used and recommend to every newbie that comes across and asks me how I got so good.
Watch Commentaries
Starcraft 2 is so big in Korea that they have their own TV channel dedicated to matches from top players! America is slowly catching on, but YouTube is packed full of good and helpful commentaries that highlight certain strategies and lets you see how the pros play. Look up HDStarcraft and HuskyStarcraft on YouTube and just give yourself an hour or two to just go through their channels.
Study Replays/Video Podcasts
Just do a search on Google for "SC2 replays" and you'll find a ton of resources where you can find top players showing off their newest strats in their replays. Download a bunch of replays and set aside an hour or two again to pop them all in and watch. Don't fast forward the beginning because the early game is the most important part of Starcraft 2. Some people like Day9 and Sen (Taiwan) put up video podcasts where they either play live or give a commentary on a live game. Again, HUGE learning opportunity here. If you're serious about SC2, you should be subscribed to them.
Play, Lose and Watch... Then Repeat
The next step should be to take what you've learned and start playing nonstop and lose. You heard me right. Losing can get so discouraging but you have to get used to it as every pro player out there lose to other pro players. If you're a newb, then you have a fair chance at losing to another newb. As you move up the ladder, you'll have the same chances over and over again. Tip: After every loss, watch the replay. See what your opponent did and think about what YOU could've done better.
Get A Strategy Guide
I'm not talking about one of those nerdy strategy books that high school virgins carry around. Get a solid, online strategy guide and get direct tips/build orders/strategies on how to better your game. This
Starcraft 2 Strategy Guide offers free resources and also reviews one that is highly recommended.