A classic tip in a good Starcraft 2 Strategy guide is to scout your opponent
. This will help you to predict attacks and better plan for builds. You can scout an opponents buildings and armies to get a better gauge of their strength.
There are so many hotkeys you need to master that most of them are posted in a good Starcraft 2 strategy guide. You basically need to memorize these hotkeys or at least print them out and have them in front of you so you can employ them quickly.
If you are using the multiplayer function your best Starcraft 2 strategy is to communicate with your team constantly. You will have to master rushing, teching and managing your army.
Make sure that you are harvesting mineral and gas the most efficient way possible. You will learn the optimal number of workers per mineral and base. A decent Starcraft 2 strategy guide will also help you optimize the amount of gas in the refinery in relation to the number of workers.
Learning about Terrans requires learning the best strategies for SCVs, Mules, Marines, Marauders, Reapers and Hellions. Even if you learn all about those they are only the tier 1 units. There also tier 2 and 3 units you have to worry about.
The tier 3 units you should be concerned with are Thors and Battle Cruisers. Thors are very effective in groups. Battle Cruisers are not cost effective because they are so difficult to obtain.
By learning a few of these Starcraft 2 strategies you will be able to be far ahead of your competition and avoid many of the mistakes that common gamers make.