Today's tip is easy and will even save you some money. Ready? If the review site says, "Do not send unsolicited books/manuscripts," then don't!!!! I'm always amazed at the number of authors who send their books to us even though our guidelines say, and I quote, "Do not send unsolicited books to our address. All such books will be recyled - we will not review them nor will we contact you." Still, we get them. I suspect authors think once we see the book, we'll just have to review it. Not so. Even if the book looks quite interesting, if it's unsolicited, it gets placed in the recyle pile right away. This might sound harsh, but with the volume of books we get, we simply can't accept all these extra books. Consider too that each book gets assigned a reviewer who reads/reviews books in that genre. If we don't accept a book for review, it might be because we simply don't have a reviewer available for that genre.
Another tactic (and this we see more from larger publicity firms) is to send unsolicited books with a letter bascially confirming that we requested the book. Nope, not going to fool us. We keep a file on each book we accept, from the day we accept it. This might work with sites that are overwhelmed/poorly managed, but I suspect few reviewers are fooled. It certainly won't win the publicity firm any points with us. A related method is to send an email/press release saying something along the lines of "we talked last month about this new book and now, as you requested, we're ready to send you a copy." Nope, not going to fool me with that one either.
Follow a site's guidelines, don't try to go around the rules, and your books will wind up in the hands of the reviewers who want to read the book, not throw it out.