A nice quote from Terry Whalin's blog:
Publishers are looking for authors who take a proactive role in the marketing of their books. These types of authors understand that publishing is a business and the role of the author goes far beyond simply writing a manuscript, giving it to the publisher and counting on them to sell the book. It takes your effort and the publisher effort to give the book the best possible launch into the marketplace.
Read more here: The Writing Life: Five Star Reviews