So i don't really know when to put the sail up and when to take it down. Should i put the sail up while still on the trailer or should i wait till i get on the water?
If you can pull the boat up on a beach, that's probably the easiest time to do it; but I've done it on the trailer, on the beach, on teh dock, and floating in the lake. It's definately hardest to do it when you're in water over your head. 😉 It's easiest when the boat is stable and pointed into the wind; whether that's on the beach or on the trailer. 
Yeah, it can be really anoying trying to put it up OR down if you're not facing into the wind. Where I sail, everyone wheels their boat down to the beach and puts it just barely in the water to its still sitting stable on the ground but you can easily pull it into the water. Then you rig everything up and then give the boat a little shove into the water when a wave is comming and off you go. More annoying than the main though is the jib. No matter what direction you're facing it flaps and thrashes violently if there is any good wind when you're trying to take it down. I've just learned to deal with it, but my friend has a roller jib and he hoists it up in the boatyard where it's less windy and then rolls it in to wheel the boat down to the beach. Then once he's there he can rig everythign and just pull the jib back out and he's ready to go.
Most of my sailing is on a lake. I never put the sails up until I launch the boat and pull it up on shore facing into the wind. Don't put the sails up on the trailer.
Howard
Thanks for all your help guys!