Review the description of the particular CLEP exam that you wish to take and the guidelines posted regarding the exam at the CLEP website. Determine how many of the prerequisite concepts you are already familiar with and how many of them you need to review. From that point, determine how long you believe it would take you to study properly.
Navigate to the individual study guides on the CLEP website for the exam that you will be taking. Take as many of the practice questions as you can to get a feel for the exam and to determine exactly how prepared you are. If you feel inadequately prepared, head to your local college bookstore and determine what books and materials you will need to study from to prepare. Purchase the necessary materials and study until you feel prepared.
Familiarize yourself with the computer-based exam process that will be required for your CLEP exam. CLEP exams are all taken on closed-server computers at testing centers throughout the country. You can examine the CLEP sampler online. Failure to familiarize yourself with this format can lead to confusion and wrong answers on test day.