Normal Way
First, you must be in Sootopolis (Fly or Surf/Dive there if you're not). Then, you should go along with the story and it will bring you to Mt. Pyre. Go inside, through all of the passages and you should come into a room with lava in the middle. If you're in the right place, you'd be stupid not to see the big red rock monster in the pit who is Groudon. SAVE NOW! Battle it and capture it! Good Luck!
I have no Battle Strategy for this Pokemon, but here are its PokeDex Status...
Name: GROUDON
No. 199
Continent Pokemon
Height: 11 feet, 6 inches (11' 06'')
Weight: 2094.4 pounds/lbs.
Ruby Description: "GROUDON has long been discribed in mythology as the POKeMON that raised lands and expanded continents. This POKeMON took sleep after a cataclysmic battle with KYOGRE."
Sapphire Description: still working on it!
Special: Drought: Intensifies the sun's heat in battles.
Codes...
Gameshark: ???
Action Replay: ???
Xploder Advance Cartridge: 83007D220195
Kyogre
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