Things You'll Need
Instructions
Go to Lilycove City in Hoenn. Talk to the woman beside the boat at the S.S. Tidal port. The woman will tell you that it's impossible to go to Faraway Island. After lecturing the woman for discouraging you, he will offer to take you to Faraway Island.
Save your game once you arrive at Faraway Island. Navigate deep into the maze of trees and caves on Faraway Island. Within a forest, you will spot the Mew. It will attempt to hide in the long grass on the island.
Look for the Mew and follow it. Try to corner the Mew, so it won't be able to flee from you. Once you're facing the Mew, press "A" to fight the Level 30 Pokemon. Since Mew is a Psychic-type, it's weak against Dark-, Ghost- and Bug-type moves.
Fight the Mew with a Dark-, Ghost- or Bug-type Pokemon that is Level 30 to Level 40. Use damaging moves until it has 10 to 20 hit points left, or less. Don't lower its hit points to zero, or you won't be able to catch it. Throw an Ultra Ball or Master Ball at the Mew to catch it.
Insert "Pokemon FireRed" and "Pokemon Emerald" into the game cartridge slots of two Game Boy Advances. Go to the second floor of the Pokemon Center in both games. Speak to the woman behind the middle counter. Trade the Mew to "FireRed" in exchange for a Kanto Pokemon.