What can I do for the ACT?

I'm taking the ACT June 12 and I have been stressing over it nonstop. I have a CD from Kaplan for higher scoring on the ACT and I have absolutely no clue how to do most of the stuff. I have taken several practice tests online and on this CD and I can only range from 21-22. I am a straight A student, always have been. My friends always say I'm smart. I don't understand why I'm so confused while taking these. Can anybody help me out? Is the ACT comparable in difficulty to like the standard prep one you take in 10th grade because when we took that it said I would probably range from 23-26. Has anybody used this CD and then taken the test and found out the CD was harder?? Please help!!