I recommend that you consider purchasing or checking out of the library a SAT study guide. Concentrate on studying the vocabulary words and reviewing your algebra and trig. You can find some very helpful tips directly from the College Board web site at www.collegeboard.com.
I recommend you read Cason Clement's post in the law school section about how he prepared for the LSAT. I think the same advice is applicable. You need to work hard. There are no magic pills for success.