The biggest pitfall to avoid is not writing. Not writing is really, really easy to do, especially if you're a young writer. The hope that elves will come in the night and finish it for you, is a very common one to have. That is my main recommendation - you have to write, and you have to finish what you write and beyond that, it's all detail.
Neil GaimanAs a teenager I wrote to R.A. Lafferty. And he responded, too, with letters that were like R.A. Lafferty short stories, filled with elliptical answers to straight questions and simple answers to complicated ones.
Neil GaimanIf you only write when inspired, you may be a fairly decent poet, but you'll never be a novelist.
Neil Gaiman