Done it for years. First trim the hair down fairly close with one of those mustache trimmers. DO NOT touch the skin with it. Do that a few weeks at a time until you get used to it.
To shave, do it in the shower where you can get warm and soften your hairs. Then, use a new razor and shave cream. Cover you crotch with shaving cream like you would do when shaving your face. To shave, start in the direction of the hair, making sure not to shave it so close as to burn the skin just like you shave your face.
Wait each time until the hair grows back to condition the skin underneath and the hair roots too. Don't overshave it. After each shave leave it alone until it grows back like you would if you haven't shaved your face in a few days .
It will itch occasionally. That is the price you pay for 1)your member looking longer, and 2) the smooth feeling when you slide that puppy home. (if you get your girlfriend to shave too, it is pure heaven. Flesh on Flesh. Ahhh!
Eventually, you will be able to shave with, then against the hair grain in the same session which gives you an incredibly clean feeling. If your partner has done the same thing, now that really is Nirvana. Good Luck.