I apologize for the delay with my answer, it's due to my net provider...
First, I found real exam very easy. For example, in verbal part I always thought that made a lot of mistakes, because the questions were extremely simple, especially RC.
Second, as far as my preparation, I did all OG and all GMAT+. These exercises are all you need to practice. Also verbal questions from PR are useful. Kaplan
tests are far away from reality... I means verbal parts because I did not specially prepare for the Math but solve Q parts of the practice exams. Kaplan
Q is meanless because I didn't see any of such kind of DS in the real test (did 8-9 from 10 correct).
SC strategy is good in Barrons book and in materials from http://s2s.wharton.upenn.edu/wh-wharton ... msg=5423.1
You just should understand the type of error and eliminate wrong choises. Don't care about correct answer - if you draw all incorrect answers, the last will be right even if it sounds strange.
CR: I did not prepare for it, just solved OG. The questions were easy. Try some questions with word problems (where are argument, conclusion, and assumption in the text).
RC: was very hard for me at the beginhing of my study. Practice a lot... Skimming strategy doesn't work. I read all the text. The PR advice to try to explain each paragraph by your own words is good.
Third, my pre-results are 700, 650, 650 Kaplan
; 640,760(after OG, so it's wrong overestimating result) PP; 600,650,710 PR. It's easy to see that my real test's score is much better. So don't worry about it...
And finally the main advice. Don't care about really difficult questions. Probably you'll get 3-4 ones at the middle of your test. But it can't make strong influence on your score. You'd better solve correctly the rest 70 questiones. I suppose that my low Q score is due to misunderstanding easy question at the start of the test. I always begin to answer before complete to read the question... did real Q in 60 minutes but with several mistakes.