How do you trade in Pokemon?

First you need two Pokemon games that are compatible; for instance Pokemon silver can only trade with gold, crystal, yellow, red, or blue. You need two diffrent gameboys (if that's the system the game is for) and a link cable wire. You plug the cable in both gameboys, and in each game you must go to the Pokemon centre and speak with the lady that will help you link. Certain Pokemon cannot be traded to certain games, for instance: the Pokemon miltank cannot be traded to yellow, red, or blue; because it did not exist in the first generation of Pokemon, so miltank would not exist in the first three games.