the correct way i believe is to take it to a shop and let them discharge the system for you. i don't think your allowed to discharge the freon into the air. dont cut the pipes as they are under pressure. the a/c lines disconnect just like the fuel line does. you need to get a special tool from the auto part store, to disconnect the hard lines to where it goes in front of the radiator. make sure you have no pressure in the line when you disonnect them. i found out the hard way. i disconnected the the a/c line thinking they were part of my radiator and got a nice supprise doing that.
Do not just simply discharge the A/C system. It's not exactly environmentally sound. Go to any shop and ask them to evacuate the system. Probably wouldn't cost much.
It won't really hurt anything if you discharge it though. It will make a mess.