I took the GRE (standard and chemistry) two years ago, as I was applying to grad school. How much you need to study depends on quite a number of things. I didn’t find the questions as tricky as @muppetish suggests they may be, I believe that to mostly be rumor. I found it really no more challenging then the SAT. It obviously is harder, but after 4 years of college it seems like it’s no worse.
Now, that’s also 4 years of science in college, and so the math at least was a cakewalk, mostly algebra and low level calculus when I’m used to differential equations and the like. So, if you have, say, an English major you’ll probably want to study up, but i still don’t think it will require too much if you did well in calculus one and the courses before. Mostly a ‘dusting off’ sort of studying, reminding your brain how to go through the motions. But, again, this depends on how well you did. If you struggled in math it’ll require more work. But I didn’t find them all that challenging, and nothing particularly tricky.
Now, the English (general English, not lit) is a bit different, I’ll grant you. I didn’t find it all that tricky, but certainty harder (again, science major, so no English courses for several years). I wouldn’t be surprised if an English major had the same easy time that I had of math, but I can’t really comment. I’m usually good with words but some of the analogies just kicked me in the face. The new electronic version is also a pain in that it aligns itself with your progress. So, in my case, i hit about five or ten just fine in a row, then got slapped with ‘myopic’ (which i now know the definition of, so i suppose that’s good) and it was downhill from there, with a run of words I honestly couldn’t figure. But, even with that I still pulled a decent grade, so don’t feel disheartened. But i won’t say it wasn’t difficult.
Analytical was fun, actually, in my opinion. If you like debating it’s great, and a chance to flex your writing skills. If you aren’t good at analytical writing then you will need to brush up on good reading and logic skills, as you’ll be asked to evaluate statements for good logic and write an essay based on a given question or quote.
Now, keep in mind that that was my experience with next to no studying. I don’t recommended it, that’s just the way it turned out. Some good vocab studying like @muppetish suggested would probably help considerably to not have a bad experience with the English part as I did, and you should at the very least do a good brush up in any area you feel weak. But try not to think of it as some very nasty problem, or it will cause you more worry and stress then it’s worth.
And good luck @hug_of_war and @muppetish!