GMAT Strategy

Hi Guys,
Déjà vu, but only in the worst sense. I came across this community in early February of 2008. At the time I wanted to go to business school and I though take the GMAT and bang apply. Almost three years later hear I am, still waiting to take the GMAT.
I took MGMAT and took the test shortly afterwards. My score was a hundred points lower then my best test. I knew I wasn't ready and started to work at it again in beginning of 09. For some reason, and I have no clue what it is, I gave up. I just gave up.
Anyhow, when I gave up my scores are in the 600 range. I would, like everyone in this community, like to beat the GMAT. My goal is 720!
MY Question is,,,or my questions are... how do you guys thing I should start?
I have my old addition of MGAT Study Guides and the 10th edition official guides. Should I start by going over all of that?
Should I get new books to start with?
My plan was to go over all the areas in general and see where I am at with the concepts. Then work my way to timing and scoring. What do you guys think? Would be very interested!!!

Do buy OG-12.

Give a GMAT Prep test once and gauge where you stand. Identify your weak areas. And then study accordingly.