First, go to Viridian city and talk to the guy that shows you how to catch pokemon and answer "yes" to his question. Then Fly to Cinnabar Island and surf east from the poke' center. Surf up and down alot until you get to him. He'll pop up just like a pokemon would. He will have Missingno and other wierd pokemon like that. They are all at level 32.

NOTE: You will have to almost be done with the game.