Here are ways to prepare for the SAT and/or ACT from free to expensive in ascending order:
1. Do the Official SAT and/or the ACT Question of the Day every day https://sat.collegeboard.org/practice/sat-question-of-the-day and http://www.act.org/qotd/.
2. Check out the free SAT test prep at Khan Academy at: https://www.khanacademy.org/test-prep/sat
3. Shmoop is another place to find test prep at no charge if your school or district has it.
4. Use your PSAT Score Report to study for the SAT. The most recent PSAT will be returned in December or early January with test booklet and correct answers to study from.
5. Get an SAT or ACT test prep book from the library, bookstore, or purchase online.
6. See if your local community college has test prep. Some of them have a two day program (one day critical reasoning and the other math) for a nominal cost.
7. Take classes or work with a tutor through a private test prep company such as Elite, Ivy West, Kaplan, Catalyst, and Princeton Review.