Am linking to this as much for my own benefit as for any readers out there! Great post on the very hand blog Market My Words (bookmark it for further use, since they have a ton of great marketing advice for writers!) by editor Molly ONeill, assistant editor of Katherine Tegen books.
I won't repeat all she says here, but her advice is extensive and excellent. Get a web presence, understand what each type of media does for you, make a marketing plan of your own, and so on. Writers, take note!