Two things I wish I had done earlier are to write constantly and to start publishing in a single genre and age group. Writing constantly without regard for publishability would have helped me find my voice more quickly. And writing for a narrow audience at the onset would have honed my voice and audience early. Branching across genres after your established is fine, but starting narrow gives you a huge business advantage. A third bit of advice is to understand from the onset that you are running a business. Learn everything about managing a small business!