I studied for a month in a half. I know i'm not a good standardized test taker, so I thought with no work or school and dedicating this whole month and a half would be fine. I used Princeton's Cracking the GRE book and Mcgraw-Hill 6 practice test ( DO NOT BUY THIS IT SUCKS). During the actual test day, I was prepared for the math section, but NOT enough for the verbal section.
I wish I had more time to study, I did study pretty hard that month and a half, but it was not enough because I did not reach the score I wanted to. I would say 2-4 months.
I would start off easy, just memorize 5 vocab cards a day, do 5 math problems. When the test date gets closer, I would do more problems and take a FULL practice test each week for the last month before your test. Good luck!