Hey Nancy....
My preparation mostly revolved around verbal. I was especially scared of RC, and I must admit that even while preparing I didn't spend enough time on practicing more RC questions. You can learn from my mistake

. The next troublers were the SCs. CR and Math were my stronger areas.
In my experience, GMAT Math is tricky in that it requires you to constantly be alert about the current question and not be influenced by the past few questions. That is, if we keep getting easy questions, it's quite probable that our mind goes into the "easy paper" mode.... for all you know, the next might be very tricky. The reason I am saying so is, during practice sectional tests, I would often become complacent, and end up doing extremely silly mistakes. Such mistakes only got my morale down. So I would suggest treating GMAT math more as a Mental challenge. In the long run, I believe, two strategies work effectively - Know the concepts well and be super alert.
For Verbal I tried to focus on all three areas a lottt. I have been employed for the past three years and was therefore out of touch with the nuances of the subject (was busy writing programs

). RCs were a major challenge for me. I am pretty bad at RCs on economics or sociology. I tried improving my comprehension, but I had very less time. I prepared only for two months. Taking GMAT was an impulsive decision. So I focussed more on CR and SCs. At the start of my preparation, I used to rely on "sounds good" funda a little too much. But as I prepared more and more, and got acquainted with all the modifiers, participles, adverbial modifiers, Verbs, tenses, moods, diction etc, I starting getting hold of SC much better. If I chose an option, I knew why all the other 4 were wrong. This gave me a lot of confidence. (My friends might soon disown me... lols... I pick on them too much these days for wrong usage hahaha

)
I found Manhattan GMAT's and Kaplan's Verbal questions quite close to my actual GMAT. I cannot say for sure about the others since I didn't try any of those.
Books and Other Material :
-> Manhattan SC Guide
-> Powerscore GMAT Critical Reasoning Bible. (100 mars to the book. I strongly recommend it)
-> OG 10, 11,12
-> Old GMAT Test Papers.
-> Career Launcher's Maths material for CAT (Our very own "Common Aptitude Test". This can be substituted by any other CAT prep material. Just referred to the Concepts and solved easier questions)
-> beatthegmat's free resources. And those numerous posts I went through for researching the answers.
Tests:
-> Kaplan's Higher score On the GMAT (Took 4 tests, score ranging from 590 to 670)
-> Score800's 8 sectional and 4 Full length tests. (score ranging from 610 - 800)
-> GMAT Powerprep (although I got a lot of questions repeated from the OG, still it was good to get acquainted with the actual screens that appear on the GMAT)
-> Manhattan's free online CAT (620 or 630, don't remember)
AWA :
I don't have my AWA score out yet. For AWA I referred to 800Score AWA. You can also get a lot of material and good sample essays here on beatthegmat.
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If I were to take GMAT again, I would work on my Reading comprehension, Take more Full length tests and most importantly, would work on my stamina........ You see, I hate to exercise, let alone work my self out

While I was doing the verbal section, there was this throbbing pain in my head, that just won't go. Questions were seeming hazy. In the same section, I found my mind drifting from the question 2-3 times. If you still have time for the GMAT, try to increase your mental strength and take as many prac tests as you can. If you don't, do not worry... I feel, GMAT is a more a test of our mental strength and determination. Battle your fears out, know your weak point, work em and make staying alert a habit!!
Let me know if you need specifics/clarifications regarding any point in the post above. I'll be glad to help.
Good Luck for your exam!!