Beware of friction with clothes on

Very difficult. Be gentle, it is very sensitive.

Well, I mean I can unzip his jeans and stuff. I just mean that I won't exactly be in a position to pull them down to his knees. So how do I do it inside his jeans?! thanks for the help :)

Outline his penis with your index finger/hand, find the head, lightly trace circles on the head clockwise then anti clockwise. He,ll be hard in no time!

well you needt o give some details as to why you will be standing up and clothed? anyway..you'll have to pull it out before it gets too hard otherwise you will have trouble getting a big ol hard penis out of TIGHT jeans.. once its out.. just stroke it up and down.. ithink whats important (at least to me) is that YOu enjoy it too... men like to think the woman enoys stroking his manhood... and then dont be afraid to ask him how he likes it.. cup his balls with one hand, and stroke it up and down with the other.