TIP 1: Start Preparing Early
The number one best way to study for SAT math is to start early and put yourself on a regular schedule. Everyone agrees that last minute cramming for SAT math will accomplish nothing, and may even hurt you by raising your anxiety level.
TIP 2: Focus on Problem Areas
This may seem obvious, but don't waste your time studying topics you are already good at. Take some sample tests, and figure out what you have difficulty with, and then attack your problem areas. Many SAT preparation books contain diagnostic tests you can take to identify what areas you need to work on.
TIP 3: Memorize Definitions and Basic Theorems
Do you know what an acute angle is? An obtuse angle? A polynomial? You should!
Most SAT preparation books have definitions of all the math terms you will encounter on the SAT math test, and the test will contain some questions you can answer just by having these definitions memorized. Make yourself some flash cards with terms on one side and definitions on the other, then quiz yourself, or have a friend or family member quiz you.
TIP 4: Study in a Group
Find a study group or start your own. Small groups are best, but the ideal size is one you feel comfortable with. Many students find they learn more easily and just plain have more fun when they work as part of a group. Share study notes, take turns quizzing each other, and help each other with difficult concepts.
TIP 5: Use a Tutor
A tutor should reinforce the concepts you already know, guide you through difficult material, and ultimately help you to work more independently. Furthermore, a good tutor does not spend time "teaching at you", or lecturing to you, rather he/she will spend time working WITH you to improve your math skills.