15-25 grams pre-workout
20-50 grams post workout

something like that...I do one scoop an hour before and two scoops within an hour after.

You need 1-2 grams of protein per pound of body weight. You need to be getting most of your protein from your diet. Like Eric said somewhere sometime (don't remember where), you're not going to make or break your diet with protein shakes. You DO need protein after your workout though.

You need protein on off days too...your body is still recovering/growing.