Lick a tree and hope it doesnt kill you
yes trading and battling
See pokemon by battling and trading. Go on the GTS.
In any Pokemon center, upstairs. Same place for link trading and battling.
no you dont have too. link cables are only for trading and battling with your friends you need to have a gameboy advance wireless adapter to to take part in mystery events.
Sorry but Leaf Green doesn't support WIFI trading or battling
By the GTS or trading with your friends
You can do it by trading any Pokemon you don't have from your friends
it is used to allow you to ave friend to trade/battle with over the WiFi connection and you get them by trading/battling with friends in the pokecenter.
keep trading Pokemon with friends and train all your Pokemon to the stage where they stop evolving
by giving all of your Pokemon to your friends and trading back to your game.
Serebii have forums for trading, battling, news, and pretty much anything Poke-related, plus an IRC chat room.
Yes, the Nintendo DS and Nintendo DSi can link together to play Pokemon. Keep in mind that games such as Pokemon Diamond and HeartGold cannot link with Pokemon Black (2) and White (2) for battling and trading.