Note: I was an SAT tutor and eventual Center Director at a tutoring place for over 2 years.
1) READING COMPREHENSION IS KEY. This has become all the more relevant with the changed to the SAT recently. They will ask questions about the meaning of the word in a passage based upon context. Rote memorization of vocabulary (though useful in its own right) will only take you so far. 2) There are calculator and non-calculator sections for the math (I forget if it's for both tests, but definitely at least one of them). It'll be to your benefit to know the math so that the calculator is an enhancement, but not a crutch. 3) Take practice tests. There are more than enough resources available from both College Board and ACT with very real exams. Being able to answer the questions correctly doesn't mean much if you can't complete the exam on time. 4) When taking practice tests, make sure to finish BEFORE the time is up. Chances are, due to nerves and triple-checking your work on the day of the test, you will take longer to finish the test. If you can complete the sections at least 5 minutes before, it'll serve as a good buffer. 5) The essays are optional, but not really. Make sure to write the essay with a solid intro, body paragraphs, and conclusion (even if it's brief). Again, make sure you save enough time for yourself at the end to proofread. Speed-writing will cause the silliest of errors. Taking 3 minutes to read over and fix them can help you.