Promoting your book should be a top priority months before your book hits bookshelves. Unless you have established a platform, you'll want to start networking to increase interest. This is especially true if you're planning to self-publish. Don't worry, there are countless ways to promote your book before its release.
Add It To Goodreads
Goodreads is a site of writers and readers sharing their books as well as ones they've loved. If your book is in the middle of production and you have an ISBN number, you can list your book on Goodreads. That way, folks can take a look at the cover and synopsis to see if it's something they'd like to add to their shelf for future reading.
Add Teasers To Scribd
Scribd essentially is Youtube for writers. You can post chapters or entire novels for others to read, comment and rate. It may not be as powerful as getting a professional book review, but the little things can add up fast. You can also use Scribd on your site to offer friendly teasers.
Join Online Communities Such as Forums and Ning Groups
Join writer communities and take part in discussions. Share advice based on personal experience. Some sites allow you to post teasers or even promote your personal website. For those that don't you can add your website address to your public profile or forum signature. Remember, you're a part of these communities to share experiences, not to spam. Always post a reply with helping your peers in mind.
Use Social Networks
Two of the most popular social networks right now are Facebook and Twitter. The reason for this is because of how easy it is to update as well as to read updates from your peers. At a glance, you can see who's doing what and when. Go where your readers are and interact. Updating your information and informing your peers takes seconds. If you find there are days you cannot blog or share an article, these work just as well.
Update Your Blog
Try and update you blog or website on a regular basis. I don't know about you, but I love reading about other authors, always have. It doesn't have to be anything major, but try and keep the entry related to the life of a writer. If you post on Mondays, try and keep to that schedule.
However, if you find you don't have much to say on that day, it's better not to post rather than to post for the sake of posting and keeping to your routine. Remember, even if there's nothing going on in regards to your submissions on getting published that day, there's plenty to talk about when it comes to the industry as a whole. So use that to your advantage. See what agents are talking about and use their posts as inspiration for yours.