I'm not an active poster but have been an active lurker and found the advice on this forum useful, so I thought I'd share my experience.
1st test (700):
I am an engineer and a native English speaker, so at first I wasn't worried about the gmat. I figured I could study for a week or so and go score over 700. I took the 1st GMATPREP practice test and got a 670 before studying at all. I then bought
the official guide, worked through about 50-60 math problems (didn't study verbal at all), and took the 2nd GMATPREP test and scored a 720. So overall I spent about 2 weeks studying before taking the actual test, and got a 700 (Q46, V39). During this test, I realized I was far too slow at math, as I had about 30 seconds to randomly guess on the last 5 problems. I quickly did so, but this made me want to retake, so I signed up again.
2nd test study strategy:
For the 2nd try, I wanted to concentrate on speeding up in math and raising verbal a bit. So I bought PR's Crackin the GMAT, EZ Math Strategies, and
MGMAT SC (based on everyone's advice on here). I also took a few of the math challenges on here. I read through all the books, and here's my 1st bit of advice: DON'T WASTE MONEY ON THE EZ BOOK!! It claimed to contain tips and tricks for quickly solving the math problems, but all it contained was common sense and a repeat of Crackin. If you only buy one book, buy Crackin the GMAT. It contains everything you need and frankly I found the EZ book and SC book a repeat of what was in there. If you are not a native English speaker, then I would go ahead and buy the Manhattan SC book since it goes into more detail than Crackin does.
So at about this point a hurricane blew through here and my test date got canceled twice (mid-late Sep). I rescheduled my test date for November because I needed to concentrate on 1st round applications. So I didn't get around to studying for this test again until late last week. My studying consisted of skimming over Crackin again, then re-downloading and taking a GMATPREP test. I got a 710 on it, and reviewed my mistakes and noticed that I made a lot of dumb ones. So I restudied exponentials and a couple other things and took the real test.
2nd Test (760, Q49, V44):
I think a couple things helped me do better this time around. 1st of all, I am not a morning person at all and took the 1st test at 8am. Not good for me. This test I took at 2pm and felt much more awake! 2nd, I took the breaks and brought caffeine/food to eat during, which helped me stay alert and concentrate. The math seemed easy, so I thought I was not doing too well (but I've heard similar stories on here). Did not get any permutation problems, which was a waste of study time! I did finish the math with about 20 seconds to go, so that was a nice change. I think the improvement was due to 2 factors more than anything else: 1) I quickly guessed on problems I either didn't know how to solve right away or I thought would take a long time to solve. I have learned to sacrifice 3-5 questions in the middle for the sake of winning the war! I did not sacrifice any of the 1st 10 problems, as I believe these are most critical to your score. 2) I used some of the backwards solving that is taught in Crackin. As an engineer, I am used to solving things algebraically, regardless of the time it takes. During the 1st test, I tried to solve everything cause I knew I could do it eventually. This time I caught myself about 3-4 times starting to write out equations, but then thinking it would be much quicker to just start with the 5 answers and work backwards. So be sure to do this to save time when u can, even if it goes against nature.
For verbal, I just tried to remember the SC rules in the Crackin and Manhattan SC books. The CR and RC questions I believe are common sense, you read the paragraph and answer the question. So I never studied or worried about those, although they can be tricky questions so just narrow down the choices and guess. But I would not waste time studying for CR or RC.
That was long but that's about it. A couple last points: I scored much higher on the 2nd test than I ever did in practice (yes I'm talkin about practice man, practice!). In a way I think I got lucky, and don't really deserve this score since I didn't really work for it or expect it. I really just wanted a 720. Anyways, don't feel like you can't outperform your practice scores. On any given test day, if you give 110%, you can pull off a miracle!!
Last point, I was very seriously considering not even taking the 2nd test (even though I had already paid and scheduled it) since I had not studied in almost 2 months, but then I thought what the heck. I guess the moral is don't overly worry about studying, just go for it and see what happens. I'm a firm believer in the brain can only cram so much information in at one time, so just cram the right stuff in and you might not need to spend 2-3 months studying. Use the GMATPREP tests to figure out what the right things are for u...
p.s. if you don't understand the practice quote above, go here:
https://www.youtube.com/watch?v=eGDBR2L5kzI