This stuff is a lot more systematic now than it was in my own caveman days, and people may for all I know prep more.<p>However, I had a college classmate who had mediocre GREs. This was not the problem for him that it might have been, since he picked his program based on climate (no more snow). He got his Ph.D. and has every since happily taught and published. He was very good at what he studied, but not at taking standardized tests.