I think most people self-prep...start out with some good books and get familiar with the test, and then you'll know what you need to do. The best strategy/overview book to start with is Cracking the SAT (the
PR one). It has good tests too, with answer explanations.
You also HAVE to get the College Board tests. The book has no strategy and no explanations, but people here will help you if you can't figure it out!