Dude, the kids here are nuking this.
Going to business school? Take the GMAT. That's all.
As for studying, I downloaded the practice tests from the prep site. It gives you two chances to take the test. So I did one, noted where I was deficient, and concentrated on that in my prep. It's high school math and English. I spent a few days in the library before the test, refreshing my high school math. It's stuff that I guarantee you know, but might not have seen in a while. So go over it. The language portion....well, you either know it or you don't. Hopefully you have a good grasp on grammar, because this is your opportunity to make up some ground on your top-line score on the Chinese and Indian kids you're going up against. After my few days of prep, I took the second practice test and my score had markedly improved. Of note: the score on my second practice test was only ten points off my final score.
Final thoughts: The GMAT reacts to your inputs--when you answer a question correctly, you get a harder question for the next one and vice versa. That doesn't really matter, but it's fun to know. Also, GMAT is only one component of your application, but it's the one "apples-to-apples" component that exists. You're competing for a spot not with the McKinsey kids, but with the other military guys who are in the applicant pool.
Credibility: Took the GMAT in Jan 2012 (so my info may be, admittedly, a bit dated), scored 750 overall--76th percentile in math, 99th percentile in language (that's what I meant about making up ground). All b-school applications to top-10 schools, all accepted. Stayed in the Navy. FML