Are you ready? Start with Astronomy.
The link above takes you to the UCI OpenCourseWare website. Work through the questions and use the "post comments" button to ask your questions and seek collaborators.
Remember, you're not alone. When you have trouble, let everyone know. Someone will help. And don't lean too heavily on the course organizer, because our whole goal is to create a real study group - so that everyone passes the CSET!!! The best explanations often come from those who are at the same point of study, so lean on each other.