[quote=Dinh AaronMk]General learning. While not directly relevant to your writing as a dressed up thing it will help out with the background bits. General knowledge of a political system or the processes behind one or a nation's bureaucracy will help out with political drama and intrigue plots. A general knowledge of engineering processes can help frame or establish a framework in something in a believable, well-enough explained matter that you establish immersion by softening a critical reader or participant's rampant questioning of what the hell is going on.
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This is definitely one of the biggest keys. If you are going to get serious about writing, try to become a large scale consumer of knowledge. Everything you do not know is a weakness, and everything you learn is a self-improvement. When you read, try to read like you are an English teacher, finding what you like and what you don't like about everything from the way the subject matter is presented to the way the words are arranged. If somebody seems like they would like to gush about some topic they know, ask questions and seriously think about what they say. Doesn't matter if it is astrophysics or the finer point of bagging groceries. 

And don't avoid learning about shit you already know. Different perspectives are what give you a three dimensional idea of how the subject works.