Answer:
I have taken and passed 17 CLEP exams, plus 7 DSSTs, so I think I can definitely speak to this issue. My overarching strategy for most of my exams has been to study the subject using an online flashcard-based study resource such as www.SpeedyPrep.com, as well as sometimes a supplemental resource just to play it safe. The other thing I do every time, is to take a practice test from the CLEP Official Study Guide (http://store.collegeplus.org/product.sc?productId=6&categoryId=8) to make sure that I am ready to take the test.
On test day, go take and pass the test. Use standard elimination tactics if you aren't sure on a question, and answer every question! Never leave a question unanswered, as you are not penalized for guessing, and there is always that chance that you will guess correct.
**Full Disclosure* I am an employee of www.SpeedyPrep.com, a 100% Guaranteed CLEP exam preparation site.*