Do:
Address your request in a professional fashion - Your email should be short and well written.
Make sure the reviewer is interested in your book category - Read their site and take a few days to really familiarize yourself with the types of books they review.
Mention why you chose a specific reviewer - No one likes to be "played". Make a point to find something about the reviewer that you like. There should be a REASON you approach one reviewer instead of another. Research the reviewer and be prepared to mention a specific review or blog post on the reviewer’s site that appealed to you
Let them know what materials you have available. - Don't make them guess or have to ask you if you have hard copies of the book, ARCs, pdfs, ebooks, an electronic cover.... etc.
Mention your marketing campaign. Reviewers will want to know your plans and dates so that they can schedule accordingly.
Provide a brief description of your book. - 75 words TOPS!
Follow the reviewer’s guidelines…exactly. - They are approached by hundreds of publishers and authors a week. Make sure you don't give them a reason to not pick your book.
Thank the reviewer for his/her time. - Even considering your book for a review takes time.
Recognize the reviewer might be too busy to review your book. - Over a million books were published last year. Even if there are THOUSANDS of reviewers, the math is staggering
Stop back by the reviewer’s site on the day a review posts and thank them, again, for their time and review. - Common courtesy is not so common nowadays. A thank you from the author and publisher is a MUST.
Before, during and after you send your book out for review, comment on other book reviews on review sites. - The book community is not there just for authors to stop in and get reviews. This is a vital, vibrant community that should be supported. Authors and publishers wanting to participate in this world need to get in there and really participate before they ask for reviews.
Don’t:
Spam. Ever. - Sending out mass emails with no personalization will be ineffective at best. Sending a generic request to a large group of reviewers will not get you the results you are looking for. The same goes for mass mailing your book to a mailing list without discrimination.
Ask for a good review - A reviewer is being asked for their opinion. Do not make the cardinal mistake of trying to tell the reviewer what their opinion should be.
Send your book or request to an outlet whose guidelines your book does not meet - Ever heard of the farmer who tried to teach a pig to sing? It wasted his time and annoyed the pig. There are enough reviewers out there with whom your book is a good fit, don't waste time going after the ones that aren't.
Call to follow up if they ask for email or snail mail only - Please give them the courtesy of following their requests.
Argue with or challenge bad reviews - While you may not agree with their review, it is their honest opinion, and challenging it is just tacky. No one wants to hear your negative comments about a reviewer if they decline to give a review or give a bad review. It will only make you look bad.
Send a book unless specifically requested - If you don't hear back from a reviewer... that is your answer.
Send attachments unless requested - In this world of viruses it is common for book reviewers to block any and all unsolicited emails with attachments.