Thoroughly research self-publishing options. Because self-published books typically have limited sales of between 100 and 150 copies, the trend is to go with print-on-demand (POD) arrangements. New technology has made it possible for POD publishers, who operate almost entirely through the Internet, to quickly and cheaply print individual copies for each order. Amazon offers its own self-publishing service, CreateSpace. Lulu is another well-regarded option. Once you've chosen a publisher, be very careful in choosing additional author services, which is where such companies make much of their profit. Also look into the possibility of going paper-free and focusing entirely on e-book formats.
Fully utilize networking options on the Internet. Use your private Facebook page and set up a separate one for your book. Research marketing options on Facebook but be careful about spending a lot of money on ads. Other advertising options include "Blogards Book Hive" and Google's "AdWords/Keywords." Set up an author page at GoodReads. Reach out to literary bloggers and try to arrange a "virtual book tour." Finally, don't forget to put care into your listing on Amazon and to make full use of the various author tools they provide.
Think about any "built-in" audience your book might have. For example, if you have written a historical novel that takes place during the Revolutionary War, contact Daughters of the American Revolution and ask if you can speak to the local chapter. If you've written a book that largely takes place in a real city or town, contact the local Chamber of Commerce. While bookstores are typically reluctant to sell self-published books, an independent store might be willing to carry a few copies on consignment if the book is of local interest. Some stores also have a section for local authors.
Study cases of self-publishing success. The quality of self-published books is uneven and sales are usually meager. But every year there are a handful of notable successes, and some self-published writers eventually get offers from traditional publishers. Lisa Genova's self-published novel "Still Alice" was later picked up by Simon & Schuster and made "The New York Times" Bestsellers List. Steve Almond, already a published author, used the Harvard Bookstore's "Espresso Book Machine" for a short book that didn't find another publishing home.