Do not do any preparation for your summer classes. Some people will recommend LEEWS or some books about law school, but save your money and your time.
As far as briefs go, dont buy them. You will write them yourself when you get to school, and it is an important skill to learn and develop as it helps you prepare for exacting information for your legal writing class.
And, congrats on getting into your dream school (baylor?)
make sure that law school is something you really want to do before you jump into it as it is hard to go back after you start.