Things You'll Need
Instructions
Insert an Action Replay or GameShark device into your Game Boy Advance, and turn on Pokemon Emerald.
Enter the appropriate code. The Aurora Ticket (483511F5 E6C8E537) is for Birth Island. There, solving a simple puzzle will allow you to capture Speed Deoxys.
The Eon Ticket (0A6626D3 648DA17A) is for Southern Island, where you will be able to capture either Latios or Latias.
The Old Sea Map (5B1CB4D7 10FA9D05) is for Faraway Island, where Legendary Pokemon Mew, at Level 30, can be captured.
The Mystic Ticket (BE39B3A8 280987E1) is for Navel Rock, home to both Ho-oh and Lugia. Climbing up the left ladder will lead to one; climbing up the right ladder will lead to the other.
Enter the Pokemon Center in any town in the game, and receive the item whose code you entered.
Enter whichever warp code corresponds to the location of the Legendary Pokemon you are capturing. Normally you would board the S.S. Tidal at Lilycove City, but at beginning of the game you don't have access to Lilycove City. The codes for each location are as follows:
Navel Rock: 842CB8A9 F8B0149
Birth Island: 4A99A22B 58284D2D
Faraway Island: 8DEB234A 4C8DC5EC
Southern Island: 7703F025 00394020
Walk through any door to transport yourself to the location.
Turn off the Action Replay or GameShark in order to capture the Legendary Pokemon.