Reviews don’t “just happen.”

Don’t assume that just because you wrote a book someone is going to want to review it.
Too often I find that writers forget about following through once a book is published, but in reality that’s the most important time to plan for a real push to find and solicit reviewers of your book. This goes for Amazon reviews too.
Your publisher should solicit a list of potential reviewers who should be sent the book, but if they don’t, be sure to pipe up and send them a list. You can find reviewers throughout the blogosphere, or in user groups, or for tech books on sites like Slashdot, and if you have a trade title with a great niche (ala Sex in a Tent) then actively read the magazines that cover your topic and try to make connections with reviewers (Glamour, Cosmo, Outside, all fit the bill for SIT).
Very important: try to find reviewers who are definitely interested in your topic. Reviewers, and bloggers, are overwhelmed with review requests, so try to find a like-mind!
I know this sounds sort of basic, but someone just asked me today if I had seen any reviews of their book and I had to ask, have you asked for any reviews?
I promise, your publisher will be more than happy to send copies to prospective reviewers.