Just write. It's the best thing you can do. You can't be a writer if you don't write. And don't think too much. I was recently told that the worse thing you can come up with is a concept for a novel. And it's true. So many times I've spoken to people who say "I've got this idea" and then describe a concept rather than a plot. Often, concepters never finish the book because they are too frightened of spoiling the concept. I never know what my concept is. It doesn't bother me at all. I just sit down and write something.