I have a few tips here to teach you how to play Starcraft 2 like a pro. I have played Starcraft since the first version of the first game, but stopped playing and wanted to quickly get back into the game as Starcraft 2 was then new to me. So I found a few techniques which helped me avoid reinventing the wheel and get me into the diamond league as quickly as possible, soon I learnt how to play Starcraft 2 like a pro.
Watch videos of professionals playing Starcraft 2. There are hundreds out there in many different formats. I like to watch commentated games such as of tournaments so I the commentators can literally explain to me what I'm looking at on the screen because most of the time, when watching pros play it all happens so quickly I can't follow it. You can also gather some tips from them while they explain why each player is doing what they are doing.
Study replays of professionals playing Starcraft 2. If you google search for Starcraft 2 replays you will find a few websites which host replays of pro gamers playing in tournaments. Studying these are an excellent way to learn how to play Starcraft 2 like a pro. I often watch these and set the screen to the perspective of a pro so I can see where he's looking and what he's selecting. You can also steal build orders from these replays and see why the player has chosen the build order based on what intel he gathered from scouting.
Read Starcraft 2 resources online. The first two methods I have already mentioned are great if you already have some experience with the game, but you might not know what you should be looking for when watching professionals play. Some good Starcraft 2 players have spent the time writing articles on how to play Starcraft 2 and these will give you the foundation knowledge you need to be able to watch pros play Starcraft 2.
Read a guide for Starcraft 2. Some professional Starcraft 2 players have written a fully detailed guide for Starcraft 2 and teach you how to be a diamond league player. These guides will give you near enough everything that can be written about to help you play Starcraft 2 like a pro including build orders, strategies, unit explainations, micro and macro techniques. This is the best way to learn how to play Starcraft 2 like a pro.