you don't need to find him. what you need to do is get the national pokedex.
by the way if you want to catch mewtwo it's on route 224! i think. well that's what some other person said. he or she said that it's one out of 2,000 chance or whatever. they said mewtwo is a HE. everybody knows mewtwo is an IT. just go get the national dex. anyway gotta go. my DIALGA is almost fainted.
in lake valor after you have caught Giratina and talked to prof. rowan in sandgem
Go to Lake Verity which is in Twinleaf Town.
It depends on how far you are with the game.
You can't find it in the wild. You can only get it from Proffesser Rowan as your first pokemon.
breed an electabuzz if you want an elekid in Pokemon platinum
Prof rowan is only in diamond and pearl and platinum.
you can not get a master ball in Pokemon platinum only the one professor Rowan gives you
find all 210 Pokemon on sinnoh pokedex then visit profeser rowan
You get Pokeradar from Professor Rowan in his lab after completing the Sinnoh Dex.
in lake valor after you have caught Giratina and talked to prof. rowan in sandgem
first you have to finish the sinnoh pokedex.then you show your work to professer rowan
Go to Lake Verity which is in Twinleaf Town.
you cant find it, you have to see all the Pokemon sapphire.
It depends on how far you are with the game.
go to http://www.serebii.net/platinum/nationaldex.shtml. Scroll down and you will find each pokemon, their location and which trainers have them
once you get a pokeradar (obtained after you fill in your pokedex by seeing all the Pokemon and then go to prof Rowan) go to the west of route 211 and use it in the grass. its hard to find though.
Look In all the Towns And Iron Island And the Pokemon League! PS. also Check The safari Zone And after you Find all 210 Pokemon, Talk To Prof. Rowan and Prof. Oak Give You The National Dex After His Talk With Prof. Rowan. P.P.S also Go to the gyms And Battle the trainers there!