I'd also recommend making a study plan - students who have a written plan of attack are much more likely to actually put in the work.

You have six weeks. I might suggest something like this:

Week 1: Take a practice test and review basic grammar and math rules; purchase a prep book and study tricks and strategies
Week 2: Do (and study) first 1/4 of problems in GMAT Official Guide, aligning each problem to strategies you learned in whatever test prep guide you purchased; take another practice test
Week 3: Do next 1/4 of problems, take third test
Week 4: Do next 1/4 of problems, take fourth test
Week 5: Do last 1/4 of problems, take fifth test
Week 6: Study weakest areas as final prep for the real GMAT this week!

That's just an example, but it gives you a place to start. Good luck, and come back with more specific questions when you have them!