Well, unless you're a great standardized test taker, it usually takes 2-3 months to prep, especially if you're aiming for a 700+. How did you do on your SATs?
Plan on spending 2-3 hours a day (or 4 if you're really taking it that soon) doing practice questions, and do a full practice exam, timed, each weekend. Thoroughly review your answers, including the right ones, to pick up patterns and more quickly figure out the test. Keep an
error log (there should be a sticky post about that somewhere on here).
I would start with Cracking the GMAT from the Princeton Review (best strategy book on the market), the 11th edition of the Official Guide (not the 10th -- too many years too old, and quant's gotten a lot harder), and the Powerprep tests that you can download free from
https://www.mba.com.
See you you're doing over the next few weeks, and ask for help in the forums when you need it. You'll need to work hard to get 700+, so I'd get started.