The best thing is to take the practice tests that are available in the GRE preparation books. You can buy these books in any bookstore. In recent years, a number of our students who have taken special courses for the GRE have tended not to do well. Of course, it is impossible to say how they would have done without the course. The best advice is that, unless you don't care about the money, prepare on your own and consult with the Career Planning and Placement Office.
Most schools require three letters of recommendation.
You should ask faculty who have taught you. You should let a faculty member read your cover letter before sending it. Many schools will describe what it is that they want in the personal statement. In most cases, this involves a statement regarding your goals, why you're interested in the program, etc. Also, some students write about how they are interested in psychology because they or some family member had a mental illness or emotional problems.