Applying for optometry school, tips for the OAT?

I've been having issues finding OAT study materials that aren't crazy expensive. I've looked through half-price books, and I picked up a DAT book that covers biology, general chemistry, and organic chemistry. I also found an MCAT study book that focuses on physics. I went to my local Barnes and Noble and found an OAT study book with 2 practice exams, but it's just practice exams and no refresher material.

Any tips for taking the OAT?