Study the
MGMAT guides, but definitely do not rely on the
MGMAT CAT exams for practice. Stick to OG12 and
OG Quant. books for practicing actual GMAT-like questions.
Also, I bought a 5 pack of post-it notes (w/ "Super Sticky" adhesive) and wrote every formula or equation down and posted it on my wall. It was great for quick reference and eventually I began removing them as I started to memorize them. I used some sort of color coding system where green stickies were important and blue stickies were of medium importance. Sometimes I found myself re-writing the same stickies and having 3 similar stickies, which told me that I need to figure that concept out and commit it to memory.
It was very messy, but helped me out alot. I was horrible at math in high school and college, but after studying for the GMAT (and as of recent, working as a math tutor for HS students) my math skills have improved and I feel smarter and am able understand math based concepts a whole lot faster.
Spend the most time on Number Properties and get them down! Number properties are the most basic math skills which the rest of the
MGMAT books will build upon. Also, the one on Rates and/or exponential functions (word problems?) and Geometry are good too.
Once you start hitting 35-40q on CATs, take a break from quant and start reviewing verbal.
I CANNOT STRESS THAT ENOUGH! Do not forget Verbal. You will feel like you need more work on quant, but the fact is you will eventually hit a wall and your quant comprehension/learning and score improvements will begin to slow down and even regress. Once this happens, STOP PRACTICING QUANT and move on to verbal. (Of course this is only if you are reviewing quant and verbal separately)
Also, do not schedule your test until you have gone through the
MGMAT guides and OG12. Once you've completed OG12 and the
MGMAT books, then schedule your test and practice with the
OG Quant and Verbal guides in the months/weeks leading up to your exam.
Good luck to you and let me know if you have any questions or run into any problems!