I have yet to meet an author or illustrator whose favorite part of the business is marketing, and if given the choice, I would far rather help promote a friend's book than my own. So that's one of many reasons for cultivating a close community of author and illustrator friends--best in person, but also helpful and far-reaching through professional organizations, SCBWI, Facebook, and other online sources (such as goodreads, amazon reviews, etc.). Word of mouth is an amazing vehicle.
I do not have as many productive ideas as Christy and David have shared, but shortly before ROAD TO TATER HILL (which is set in the North Carolina mountains) was released, I did do a thorough search of all the independent book stores in the state of NC (not my home state), with the idea that they might be my best opportunity for book sales. Who doesn't like to read a book set in a place familiar to them? Before the actual release, my husband and I planned a road trip through NC, stopping at as many "indies" as possible. I always had to bolster myself before I went inside, armed with some ARCs of the book and postcards I'd had made with the book cover on the front and a nice review and the ISBN on the back. I introduced myself as an author (stating Delacorte Press/Random House as the publisher, so they would know it was not self-published), left a postcard, and, if the manager/owner seemed particularly interested, I left an ARC, as well. When the book was actually available, I followed up with a mailing (the same postcard), which I hoped would be a good reminder. I don't really have a way of judging how successful this was, but my book was nominated for a SIBA (Southern Independent Booksellers Assoc.) award that fall.
Another very successful effort was getting in touch with the current professors of Children's Literature at Appalachian State University, not only my alma mater, but also located in the very vicinity of my book's setting. I gave two professors copies of the book, which they read, enjoyed, and subsequently used in their curriculum. They invited me to speak to their classes, not only that semester (Fall 2009), but every semester since! One of the professors nominated the book for the NC Battle of the Books List (which it is currently on) and has also helped to spread word to NC librarians and teachers, resulting in many school visits.
Patience is a word to keep in mind. When a book is launched, we (especially new authors) think we have about three months for the book to take off and catch readers' eyes. After that, the publishers move on to their new lists and can't afford to do more to promote a book from a previous list. And it's sad that to be considered for major awards, books have to be noticed within their year of publication--especially hard if they are released late in the year! However, I've found that my readership is growing now in the third year since publication, and I am receiving even more letters from readers as time goes by. Thank heavens those state reading lists give a little more leeway, but usually not more than three years.
Ten years after publication, my first co-authored book, BROKEN DRUM, was picked up by Scholastic Book Fairs--very unusual! And because it had been out a long time, Scholastic decided to give it a new look/cover and a new title, DRUMS OF WAR, which ultimately gave it new life. A year later, they licensed a second co-authored book, REBEL HART. Now BROKEN DRUM has been optioned for a film and is currently under development with the hope it will be released within the 4-year window of the 150th Anniversary of the Civil War.