You will require at least one friend to beat you home and conceal themselves around the bedroom (under piles of clothes, behind curtains, under the bed, etc).
When you arrive home with your fat ugly trophy you must persuade her to come to bed with you, this is not usually a problem with the fatter more rancid looking catches.
Dispite how ill it might make you, you must engage in sexual intercourse as soon as possible to prevent your friends from getting cramp in their small hiding places...
The main event comes when she approaches orgasm (or before but this way usually gets a better effect). Remember you must be in the doggy position for any of this to work right..
As soon as she begins to climax, yell RODEO!!! at the top of your voice, at which point the room should explode with hidden friends yelling at the top of their lungs (with flashing cameras for best effect) causing your fat assed partner to start rocking and bucking like an angry buffalo trying to escape the flashing cameras and hide her big naked ass. The trick is to stay on her for as long as possible after the initial yell.
Typically, a man does not want to do this to a girl he wants to remain in a relationship with.