[demonbuttercup]

well there you go. you answered it yourself.
if you rub the perineum (little area between the scrotum and anus) it supposedly helps stimulate the prostate and this feels good for guys, from what i hear lol.
otherwise, you stimulate it anally w/ a finger, dildo, whatever.

im sure its pinpoint location would be different for every guy. you would just have to rub down there and see what feels good.