You know what I think the single best thing an author can do to market her books?
Write a damn good book.
Don't save anything for the next book, don't hold back, don't be polite. Put it all out there on the page and let it speak for you and to your readers.
Then, well, you do what you can to let people know about your book. Most of us don't have the resources to make our books a hit. What do publishers do for their big authors? They give away thousands of books (See: Amanda Hocking's story about her traditional publishing experience.) They get articles in major news outlets. They tell book wholesalers the print run is 200,000 and that they want front-of-every-single-store placement.
Julia Quinn, I'm told, when mostly unknown, hand-made ARCs and sent them to bookstores and readers everywhere. This worked.
You know why?
Because her books were delightful.
You could do the exact same thing, and if your book is not delightful, or gripping, or what have you, it's a waste of time and money.
Start with a damn good book.