The SAT is NOT an IQ test! SAT stands for Scholastic Aptitude Test and really shows what skills you have acquired, how good you are at taking timed multiple choice tests, and how good you are at taking THIS timed multiple choice test.
It's key to prepare for the test by becoming familar with the types of questions it asks and how it asks and answers them. If you begin to prepare for the test early, you can recognize areas of weakness and acquire the skills they are looking for.
Take advantage of the PSAT. The PSAT is a shorter version of the SAT, but of about the same level of difficulty. Taking it at your school will prepare you for the experience of taking the SAT and its scores are not sent on to the schools to which you apply.