Writing on the Writer Beware blog, Victoria Strauss points out that it's important to put into context some of the more extraordinary self-publishing successes that are being hyped in the press.
She writes that generally these books are written by "successful, established writers--in some cases, best selling writers--who possessed substantial platforms and self-promotional savvy before deciding to bypass their commercial publishers and self-publish. These are advantages that your average debut author, who must begin from scratch, or your long-time midlister, whose small audience is mainly characterized by the fact that it never gets much bigger, don't possess. What Seth Godin can do, in other words, probably isn't what you can do."
Neither she nor I are suggesting you shouldn't self-publish, just that you need to have a realistic picture of what it takes to sell your books.
I'm just starting to put together a program that will help authors--self-published or not--build a platform (that is, a way to reach potential readers effectively). I'll tell you more about that when it's closer to being done. In the meantime, there are also two chapters in "Your Writng Coach" (Nicholas Brealey Publishing) about conventional and unconventional ways to market your writing.