Get as much feedback as you can. Study the techniques of writing, over and over again; and - most important - live life. Have something to say. Keep growing as a person.All the books that are important to me evolved from the author's real-life experiences. (Cervantes never would have written Don Quixote if he hadn't had so much failure, and was then was forced to become a tax collecter and to travel the roads of southern Spain.)
I wish I had know that years ago, when I first wanted to be a writer, but isolated myself from so much of the real world.