How good at math are you to begin with? If you generally get As and Bs, you probably don't need a tutor, just more practice. Taking lots of practice tests, and reviewing your errors, will do wonders for your score. (I didn't prep much for my first SAT and am too embarrassed by the results to post my score!)
Blue Book tests are great, but I don't think they're enough. They don't come with SAT strategies or answer explanations, so I would get additional books. I like to recommend Princeton Review...I have a battery of their books (SAT, ACT, SAT II and I think some AP stuff; it's a scary sea of red!) and I think they're the best on strategy. Their tests are also closer to the real thing than other non-official tests.
I'd start taking practice tests, reviewing your results by question type, and then focusing on weaknesses. Keep at it and your scores will go up.