Do everything you can for your books. Visit your publisher, track your book closely through the publication process, and be of whatever help you can with cover art, catalog copy, and publicity materials. Be a professional but relentless advocate for your book. Promote your books. The most common reason authors become disenchanted with their publishers is lack of promotion.
Most books have a one-month window of opportunity to sink or swim in the continuing deluge of books.
That window opens on pub date when books are in stores and reviews start to appear. Large houses are looking for writers who are ready to pop, who are ready for the big time. For most nonfiction aimed at a wide national audience, the authors' ability to promote their books will usually be far more important than the content of their books in determining the editor, publisher and deal they receive for them. For serious nonfiction books, the ability of authors to promote their work is less important. The ability to promote books is becoming as vital for novelists as it is for nonfiction writers.