Sign up for RSS feeds on Fantastic Fiction or the author's or publisher's web page. Fantastic Fiction allows you to search by author name or book. The site takes you to the author's page where you can click on the small RSS icon. This takes you to your default RSS reader and will alert you to any scheduled book releases from that author.
Search for your favorite author's website or Facebook page. Most allow you to subscribe to email alerts, newsletters, mailing lists and even podcasts.
Search the websites of your favorite authors' publishers. Large publishing houses often allow you to subscribe to their newsletters and email announcements.
Check out AuthorsTrack for information about where and when your favorite author will be appearing in your hometown. These visits usually coincide with the release of a new book.
Search online booksellers, such as Borders and Barnes & Noble, for new and upcoming book releases.