I followed some links recently from Dave's blog to GMAT forums. They seem very useful, but I am glad I didn't spent time on those when I was studying for my test. Nothing against these excellent resources, but I was quite intimidated when I read thru them last week. Every third question posted seems to have someone replying that they got it in 5 seconds using a particular method. And there are replies that need 10 more posts for clarification of what was being done. I would probably be going around in circles trying to figure out all the information.
Absent these sources, my strategy was pretty low-tech, especially for quant. GMAT questions can be bunched into categories - ratios, permutations, trigonometry, etc. All problems of a kind can be solved similarly. Once I found a way to answer a particular type of question, I worked on a bunch of related questions using the same technique. For e.g., I would convert percentage problems into real numbers using 100 as the base. This is not the most elegant or time saving way to solve these problems, but it was one I was comfortable with. So, anytime I saw a problem of this type, I knew what I was going to do. That settled, the next thing I worked on was speed. Doing problems over and over made me faster. I think that if I had tried to master every new technique of solving a problem that I came across, I would not have been that effective. Essentially, I took out the 'how' of solving a problem from the exam and concentrated on doing it quickly, giving myself time to check my answers and finish in time. Obviously, there are the surprises, and those were the tough ones for me.
Of course, each person has a different way of approaching the exam, and this was mine.