StarCraft 2 has been selling like hotcakes in the short time since it has been out. Just like the first game, victories are measured in speed and alertness coupled with a full and complete understanding of the game and the various StarCraft 2 tricks which are both unique to it and which are similar to the first game. To give you a head start over your competition, let's look at the best StarCraft 2 trick right now.
First, it's very important that you limit your focus to one race of the three. It doesn't matter which because each can be used effectively against any other race if you know what you're doing. The point is to not spread yourself too thin and instead practice and learn everything you can about one race so you can be most competitive rather than being just decent with all three which is a common mistake which a lot of players I've known have made and continue to make.
As an extension of this point, each race comes with their own units and buildings. This means that each race has their own set of build orders, as well, which is a very important StarCraft 2 trick to keep in mind. The build order is obviously the order in which you build up your base and forces and depending on what strategy you use your build order will differ accordingly. In other words, you likely create a different set of buildings and units if you're on point to launch an air attack versus an early rush or basic ground attack. By focusing on one race, you can learn how to most quickly and efficiently build whatever kind of units you want so that you can develop your attack quickly and effectively.
It's also important that you consult a StarCraft 2 trick guide but rather than the official guide which they sell in stores, you should look into getting an online guide or joining an online membership site. There are a lot of guides and sites springing up developed by professional players of the game including beta testers and top tournament players from around the world who've spent virtually every hour of every day since again was in beta mode and since it came out developing different unique StarCraft 2 trick and tricks with each race and unit. You won't find these latest tips from the official guide or anywhere else as these sites and online-based guides are able to constantly be updated.