Just start playing is my advice. Don't worry about your league or rank, just play games and let the matchmaking formula do its work. Focus on developing your economy. Get out that first queen, don't miss your injects and keep your money low. Delay building units until you need them, and stay focused on hatcheries, overlord, queens and drones.

Also, watch Day9:

http://day9tv.blip.tv/file/4210235/
http://day9tv.blip.tv/file/4712303/