ehoustman
I've thought about taking one of the free CATS, but I'm worried that I'm just going to waste a test because I'm pretty confident I will bomb it. I haven't taken a math class in years, and would need a complete refresher on basic quant topics. But then again, I guess that's what practice tests are for right?

I disagree with Rich and agree with you. I wouldn't waste one of the GMAC CATs like that. Save both of those for the end of your prep prior to taking the test to really gauge how well you are doing.
I started with the
Manhattan GMAT books and just went through them, and did tons of OG problems. The
Manhattan GMAT online lectures (online videos) were immensely helpful if you have the money and time to spend. They are amazing supplements to the books, but if you're an amazing book learning & studier, then the books are sufficient for learning the right strategies.
They key is drill, drill, drill. Take the OG diagnostic, see what you're weak in or need to brush up on. Then go through
MGMAT, learn their strategies enough that they're second nature but drilling more problems as you go. Keep doing problems. Download some GMAT flashcard / quick-test apps for your phone and do them in your spare time so you're constantly thinking of how to solve these types of problems.
Doing that, I went from an abysmal 540 initial diagnostic score (after maybe 2 weeks of concept review) to a 690 in practice tests within 2 months; I ended up with a 640 on my first GMAT because of poor testing conditions and anxiety. more focused studying on weak areas that I garnered stats on from my
MGMAT CATs (there are 6 you can take and learn your weak areas from) pushed me to a 740 on the GMAC diagnostic, and a 710 in the actual GMAT test, which I took in my ideal test conditions (later in the day, after work, no caffeine).