Have you figured out the way that you learn best? Here are some suggestions for studying depending on your learning style:
Testing yourself over material you've read is a good way to determine whether you've actually learned the information. The two websites below give you the free tools to create flash cards and quizzes to test yourself before the real exam.
As you've probably already noticed, reading a science textbook is not at all like kicking up your feet and reading a relaxing novel. It's hard work! The resources below will help you read science textbooks more effectively.
Chunking is learning information in categories, rather than trying to memorize a myriad of small details. The human brain has about 7 slots for information in the short-term memory, so you want to put more than a single fact in each slot. Try some different organizational schemes for chunking to see what works best for you. Here's an example: