General Amazon still has 80% of the market. Ebooks are ever-fresh. They don't have the dead time like print books sold in bookstores. Creating a backlist is key to building readership in a saturated market. Bookscan numbers matter.
Creating an ebook Do hire an editor, or at least a copy-editor. Do hire a cover artist to create two images, one midsize, one optimized for thumbnail size. Do *not* try to run a PDF through an automated ebook converter. If using Smashwords, follow Smashwords style guidelines. Download an emulator for the different formats to check what the book looks like. If putting out an ebook short story collection, include a couple of short stories that were published well, plus new content.
Useful blogs for self-publishers: * J.A.Konrath * Terrible Minds * Jim Hines
Publicity Build a marketing checklist! Things to include: Goodreads Send it out for reviews! Google "genre" review sites, email every review site that relates or might have reviews. No review site too small! Kirkus Review, costs $500 for self-publishers but might be worth it. Booklending.com IndieReviewer.com - a database of bloggers Kindle boards Nook boards
Finally If you get a publishing contract, make sure it includes a reversion clause and a definition of what out-of-print means--usually 5-10 years or fewer than x sales per year. Ask for production files (includes cover art and professionally produced ebook files) reversion or the ability to purchase them should the book go out of print.