I agree w/ muchmass as far as how much to take. you can work your way up to 3x a day if you can handle that much caffeine. i myself cannot handle 600 mg of caffeine in one day.
I think I read that a ratio of 3:1 is best caffine to ephedrine. I do two days on and two off and then clen on the other two days for a few weeks with good results.