Practice makes perfect!
To learn more about the SAT and how it differs from the ACT, click here.
There are 6 downloadable pdf versions of full past versions (used until Dec 2015) of the SAT here. Access new SATs (starting in March 2016) here.
The older tests are reportedly less accurate, so use them mainly for practice and not to predict your score. The newer tests are more accurate indicators of what score you should obtain on the official SAT. Just simply click and download the pdf.
Contact WorldWise Tutoring to have a tutor help you utilize these practice tests to the highest ability.