The "easiest" CLEP exams would be the ones where you already have some knowledge of the content. I would suggest you visit the CLEP website (CLEP - College Level Examination Program (CLEP) -Save Time. Save Money. Take CLEP | College Board CLEP Site
) because you are going to find not only background information about the program, but also the exam descriptions for each exam. These descriptions will be key for you because you can then compare the listed content breakground to what you already know. The foreign language exams are limited to Spanish, French and German.
In regards to your other questions, the CLEP exam fee is currently $80. You can only take the CLEP exams at a CLEP test center. You will find a link on the CLEP website that says "find a test center" so you will see a list of test centers in your area. It is then up to you to call these test centers to verify that they are "open" test centers (allow any students to take the exams at their center and not just their students), when they test, how to register at their test center, any additional proctor/admin fees, etc.
CLEP exams are not scored out of 100 -- they are not a percent! Many people are confused about this method of scoring (called scaled scoring), but all you need to know is the range is from 20 (no answers correct) to 80 (all answers correct). Please make sure that you check with your university to find out exactly what their CLEP policy is -- accepted exams, passing scores, credit limits, etc. There is no such thing as a standard passing score for instance, though many do follow the ACE (American Council on Education) recommendation of a '50' being a passing score. Always, always, always double-check!