If you're planning on applying to English grad programs, don't worry as much about the math sections. I mean, don't bomb them or leave them blank, but don't concern yourself with scoring a 700 on them. Focus on the analytic and verbal sections.
For vocabulary, make flash cards. There will be words you don't know, but don't make cards for every single one. You should be able to find a list of the hundred words (or 150, something like that) that show up most often. Make cards for the ones off that list that you don't know (just to make sure, look up definitions for all of them). Also, the verbal section will ask you content-related questions about textual passages, some of which can be very long. Learn how to read them quickly and efficiently, since you'll waste time re-reading. Try and pick up on key moments of the passage, such as when the author makes or refutes a point.
Analytic is more difficult to study for, but if you don't have trouble with critical thinking you should do well. You'll need to flesh out a logical argument of your own making, as well as pick apart another argument (i.e. determine if it's strong or weak and point out its errors; most arguments in this section usually have glaring errors).
Finally, take a practice exam. Then take another. Then take another. Take as many as you can. The GRE isn't about learning the material as much as it is about learning how to take the GRE. Once you learn how they ask questions, and the kinds of questions they ask, you'll perform better.