I actually tutor the GRE exam during the summers (when not teaching at the University) and I got an 800 verbal back when I took it myself (when they used an 800 point system). In my opinion, the best way to study for the verbal portion of the exam is to take practice tests-- buy practice books and/or sign up for one of the online sites that offer sample computer tests (there is a small fee, but it's worth it). You can access one or two on the GRE website but, after that, you'll need to purchase sample exams. Acing the GRE is only 50% what you know (i.e. vocab words, etc) and 50% about knowing how the test works, the patterns they use, and how to guess when you come across words you don't know. It's also a timed exam, so being extremely familiar with the format and the strategies will help so that, when you do come across a question you don't know, you can take your time without having to rush. I would say that, about 50% of the time, even when you don't know the words, you can deduce the right answer simply by relying on strategies/common patterns used by the testing company. This is especially true since the GRE uses analogies, antonyms, and words in context (in a paragraph). It never just asks you for the straight definition of a word.

So, do tape words around your house. Do write your own flash cards. BUT I would spend a lot of time taking practice tests and reading about (and practicing) the strategies outlined in those practice test books. They work! I've had plenty of students with excellent vocabularies who have struggled with the exam, just because they weren't familiar with the format and didn't know how to "take the test." I'm not saying that I think the GRE is a great tool to judge an applicant's suitability for PhD admission-- I don't. Sadly, just like the kiddos in the public school system, it's more about how well you know how to "beat the test" than it is about what you actually know. Given this, I've also had several students whose vocabularies were lacking, but who did very well on the exam because they studied "how to take the test."

Have you taken sample exams and do you know what you are typically scoring now?