<p>Check their website and see what topics they cover?
Also some practice tests should tell you how the structure is.</p>
<p>The first round of the tests are usually just for getting used to the format. Once you have done the SAT and the ACT, you’ll choose one you felt more comfortable with (and feel you can improve on) and then just practice regularly.</p>
<p>That’s not to say you shouldn’t be prepared, but just don’t push yourself too much and try to get used to the formats and see what fits you.</p>