It would seem to me that the techniques that you are using may not be suitable for you. Some people may find Kaplan/Princeton's tips useful, but I didn't except for their break downs of the types of questions...other than that, I don't think doing as they proposed (5 steps or something) would really help me improve. Try looking into other prep materials that you haven't explored. I looked into tons of prep guides (well, I skipped the obvious bad ones like Barron, Real etc), but that doesn't mean I'm using all their techniques, I'm just picking a few from each that helped me. Again, if you don't know why you messed up on certain questions, look at their explanations.