you can trick your breasts into thinking that your baby's just not eating as much anymore by pumping only a few times a day, when you just can't bear the pressure anymore. then you can reduce the frequency and your breasts will get the message not to produce so much milk.
i didn't have the patience for that so i went cold turkey. warm showers helped me and i would do some manual extraction in the shower. it's best to do only if you can avoid triggering your letdown since that will just put more milk in your breasts anyway. i was lucky enough not to have a really strong letdown so i got away with squeezing some milk out and getting a little relief.
i'd heard about breast-binding and tried it for a day. it felt better not to have the milk sloshing around but the more i thought about it, i realized that you're trapping milk in your ducts so there is more of a chance that the milk will grow bacteria and you'll get mastitis. now that is painful.
it sounds weird but refrigerated cabbage in your bra feels good. just stick it in there until it warms up and switch it out. you could probably put anything else cold and it would feel good but i thought i read somewhere online that the cabbage is supposed to help stop milk production.
you can eat/drink all the things they tell you inhibit milk production. the only one i can think of at the moment is sage tea.