Studying

Kaplan stuff across the board is pretty bad.

Official materials for actual practice are the best. Ther's no beating the actual practice tests and questions to really get a gauge on how you're doing.

In terms of learning the content, for math I like target test prep for a concentrated focus on Math. Magoosh is pretty good too, a little more simplistic, but still good.

For verbal content, the Powerscore bibles tend to be pretty good, but otherwise you just have to read a lot. For GRE, you just need to crank on vocab, for GMAT you need to crank on learning grammar structures.

Manhattan is ok across the board except for verbal. I'd avoid it for that. Their in-person classes are ok, but I've found in general that any big box test prep is catering to the lowest common denominator students. Given that everyone on this forum is probably targeting a 700+ type of score, I feel like the Manhattan classes themselves won't get you there.

My general strategy for the tests is to study the content if you need to (ie learning geo formulas and vocab) do a bunch of porblems, mixing in both realistic timed sets of official material question as well as just a larger volume of magoosh and manhattan questions in an untimed environment, with a focus on reviewing your answers and fiuring out the multiple ways to solve each questions. Do intermittent practice tests every few weeks where you try to block a few hours and do a mostly realistic practice. If you need an extra bump, find the best local tutor and do a few sessions to focus on whatever you need help with.