I think it depends on your tolerance too. The first time I smoked I got totally wasted from less than half a joint. I didn't even feel stoned until the joint was finished though, it sort of crept up on me. When I smoke now I feel it after about 6 or 7 puffs or hits or whatever you call it. You know that feeling you get around your eyes when they start to get heavy and stuff. I breathe it in really deep and hold it for a sec. By the time I've finished the whole joint I'm fucked, can barely move from the chair.