How in the world do you people retain all those study questions?

[PeteDude]

How much you absorb for a given test may also be dependent on what grade you're shooting for. If you're taking an exam that provides a letter grade (e.g. DANTES, ECE), then it may be worth studying EVERYTHING if you're after an A. If it's a pass/fail scenario (CLEP), there will be no difference in grade no matter how high the score is-- in which case you can use other tools (e.g. Peterson's tests) to assess your knowledge against a passing baseline and work to that level.