In order to succeed on the SAT, you have to prepare for it. Virtually no one can go into the test and expect to get an acceptable score without some kind of preparation. In fact, it has been shown that students that prepare months ahead of time are those that receive the highest scores. It is just a matter of knowing where to start.
If you are not sure what your first step should be toward preparing for the SAT, you can talk to your guidance counselor or you can turn to the Internet for answers.