im assuming you mean raiko, and you cant catch him in leaf green or fire red. you would have to trade from another game.
you dont
catch it in the wild
You can't.
1st of all it is Raikou and by roaming Johto
you catch raikou on the last gym leader in the kanto leaders and you catch uxie in vermillion city from
catch pikachu in viridian forest and then use a thunderstone on it. same for firered and leaf green. ( kkrenzke says- ) they mean the legenday electric dog pokemon, your thinking of Raichu the evolved form of pickachu.
look around for Suicune/Entei/Raiku
You can catch Mewtwo, Suicune, Entei, Raiku, Ho-Oh, and Lugia.
the ultra ball is what i used to catch it...but you could use the master ball after you get it
you have to beat elite 4 then catch all unowns.
You just need one of them.
You have to trade or migrate. You can't catch them in diamond.