I just did my CFAT back in December, I am in grade 11, and during grade 10 math, scored something like a 54. The CFAT isn't designed to fail you, a lot of people who went into the test with me, were nervous as they thought the army was 'out to get them' or that they wanted you to fail. Quite the opposite I found, the links in other posts to IQ tests and other such things are great, I studied them a few weeks prior too, and brushed up on basic math (division, percentages, algebra, multiplication, addition, subtraction etc...) and I did fine. The test isn't a 'breeze' I found, but it isn't insanely difficult, sounds contradictory, but it all depends on your personal and academic strength's and weaknesses.
The best tips I have found on this site, that helped me were
1. get a good nights sleep (IMPORTANT!)
2. have a good breakfast
3. give yourself PLENTY of time to get there, that way you aren't stressed for time (once you get there you can relax, have time to ask questions, washroom etc...)
4. Study beforehand
5. watch the time left on the little clock
6. RELAX <--- most important, many people (including myself) can get a little nervous on written tests when they see its timed. RELAX, and do what you can, if you have to make a guess, make an educated one. a guess is better then nothing
Like I said, I just passed math last year, yet on the CFAT, I qualified for every single trade and was sworn in last week RO21 (reserve) artillery - apparently one of the more mathematically demanding combat arms trades, so I'm told.
so..... RELAX, be confident, prepare, and you'll do fine.
MattP