I have written about my experience taking the GMAT and what resources to use. I scored a 750 while studying for 6 weeks. They can be found here
My advice is after you familiarize yourself with the GMAT Format, try a few practice questions and briefly review the topics. Soon after, take the practice test. I recommend taking the first practice test from GMATPrep software that is free on mba.com (these are from the people that make the gmat). Take the practice test (you can skip the essays) and from your score, see where to go from there.