I've just finished my first revision of Storm Warning, my collection of short crime stories set on the fictional Caribbean island of St. Crescens, and I'm busy sending out queries to reviewers who might be interested. I find this part as excruciatingly difficult as submitting queries to agents and publishers. So far, I've sent out about thirty requests to various bloggers and have gotten interest from about five. That's a bit disheartening but, of course, I'll keep on trying.
I came up with my list by Googling blogs of mystery reviewers. Once you've done that and found a few likely candidates make sure to see if the blog carries a list of links to other reviewers. Quite often, bloggers will have a list of blogs similar to theirs on their sites or they'll participate in certain memes and you can pick up a lot of other names and addresses that way.
One thing that's really important is that you check the reviewers review policy - they might not review in your genre or they might not be accepting any new books for review at the moment. I can imagine that it would be annoying to receive a lot of requests to review romantic comedies when you only read horror. In addition, some bloggers won't accept from self-published writers or don't want ebooks so do check the policy out carefully.
Also, keep a list handy of everyone you submit to so you don't end up submitting twice, as the more absent-minded among us might.
Oh, and, if you can, make sure to post the cover and blurb up on Goodreads or Shelfari as some bloggers will check you out there first.