Websites, blogs, and social mediaUse your blog
If you haven't started up your blog already, this is the time to do it.
www.blogger.com is free and easy. Set it up with a jazzy title (it took me several goes before I was happy with "World of the Written Word" ... and I still wonder about it).
Write something at least once a week. Use journo-style headlining; make it snappy and interesting. Human interest tidbits work well, though bulletins from publishing news and gossip help to build up an audience, too. Illustrations are a must: you can get away with a few posts without pictures, but to have them all like that turns your blog into a bulletin board ... boring.
Inter alia .... DON'T tell the world that you are off on that month-long vacation. It's an open invitation to burglars. Instead, prepare ahead by creating a stockpile of draft posts; then, when you call into internet cafes, it is a simple task to bring up two or three of these and publish them, giving the universe the strong impression that you are still at home at your desk.
Once you have your audience, talk about your book. But don't talk about your book to the exclusion of everything else. Remember that it is a blog, not a stream of press releases. If you have a lot of things to say, divide them into a number of draft posts, and publish them at intervals.
Post updates on your website.
You don't have a website? If you have published at all in the United States, becoming a member of the Authors Guild opens a gateway to an excellent site builder. The basic fee is $3 a month. You could also try www.simplesite.com -- which is as simple to use as promised, but has a scale of fees. A google search will find other avenues.
These can be printed off very cheaply, from sites that offer self-design tools. I used VistaPrint, but it's a good idea to shop around.
Try to remember to carry them around with you. Have your blog and website addresses posted. Give them out as often as possible. One author I know had the nifty idea of making bookmark-shaped business cards. Not so useful when your book is on Kindle and not in print, but still worth a thought.
Get into the habit of linking your most lively blog posts to twitter and Facebook. This will help when it comes to promoting blogs about your book.
Link up with other authors and book-discussion sites. With luck, they will link your blog to theirs, broadening your exposure.
Give away books?
This, with Kindle, does not mean giving away actual print copies, of course -- the Kindle equivalent is making your book free.
Whether you think this is a good idea or not depends on you. Famous instances of writers who provided free content online include Julie Powell, who blogged about her daily trek through Julia Child recipes, leading to Julie and Julia, the first blog to be made into a major movie.
Another is Irish writer David Gaughran, who accumulated rejections for his first novel until he ran out of stamina and patience, and made the decision to self-publish. He gave away more than 30,000 books, but still managed to make quite a lot of money.
More importantly, he established a reputation. That, I think, is the major reason for making your first Kindle book (or two) free: you build up an audience that is willing to pay for books three, four, and more. If you have published enough in the traditional way to have a reputation already, then it shouldn't be necessary.
The alternative is to sign up for Kindle Select. This gives all kinds of opportunities for offering free copies of your eBook to reviewers ... and friends. People who just might put a review on Amazon commenting on your book, and maybe even saying nice things about it. The more reviews, the more attention-worthy is your book, so it is well worthwhile.