The best way to prepare for the NREMT exam is to study and understand your text book. The classes are designed to bring you up to national standards. Why pay several hundred dollars for a class only to waste more money on so called study sites?
Here is the low down on the NR test - it is a test designed to test your knowledge of the EMT curriculum, which is taught in class. Most of the test is scenario based.
At the beginning of the chapter in your book should be chapter objectives. Review these. If you can understand and correctly explain the objectives then you will do fine on the test.
Biggest cause of failure is people stressing themselves out. Relax, study your book and class notes, get a good night sleep and eat well.
Thousands of people have passed this test including me. If I can do it so can you.