honestly? years of practice.. one of a few ways u can learn control oevr your PC muscle (the muscle that you use if you tried to stop peeing in the middle of taking a piss).... if u want to strengthen the muscles you can either practice by stopping in the middle of taking a piss every time u pee and/or when jerking off, just b4 u get ready to cum ,stop, and let the feeling go away, then do it again, kinda like teasing urself, do that for like 15 minutes. trust me its cool as shit when a girl says "DAMN BOY you can last long", and watching ur girl limp for the next 3 days from soreness is worth the time it takes to learn PC muscle control i can literally cum on commmand, the coolest thing is when the girl is ready to cum, if she wants ill cum at the same time, its like 2 fucking wolves yelling in the night lol