If you're in your 20's, you will need a higher dose. If I have to guess I would say for fat burning, I would start with at least 3 or 4 iu's and see how your body responds. For size, it's going to have to be somewhere in the 6-10 iu range post workout/3 times a week.
If you are in your 30's, you should get good results at 2 iu's/day, 5 days/week for fat loss. And for size, anything over 6 iu's using 3 times per week protocol.
I'm 38 and I use 2 iu's 5 days/week.