Hey panther,
What I recommend, assuming you have the 11th edition, is to start by doing the first half of each section. Since the problems are in increasing level of difficulty, you can knock out the easy questions first, then when you're more familiar with the problems, concentrate on the medium-hard ones.
I recently finished all the quant stuff. I wanted to do it before attacking my weaksness, the verbal. Some of the earlier questions are ridiculously easy. You can go through 4-5 quant questions in less than two minutes. This situation, of course, would not happen on the real exam, so just get the easy ones out of the way, then concentrate on the harder problems.