You should

watch the head of your penis expanding as you slide your hand down. Repeat with your right hand. Now continue this act over and over, one hand then the other in a sort of "milking" action. Be sure to keep a tight grip around your penis with your thumb and forefinger as you milk down to your head, watching your head expand with blood as you repeat, one hand then the other, over and over again at a medium to brisk pace.
While milking, do not ejaculate. If you feel the urge to ejaculate, pause milking for a few moments and wait for the urge to subside. Holding back is an exercise in restraint, which will instill a sense of self-control. This milking stimulates circulation in the genitalia, and the increased blood supply is temporarily trapped in your penis. After several months of milking, your penis will begin grow longer as well as much thicker.