Instructions
Select Charmander as the starting Pokemon for your game in "FireRed" or "LeafGreen." If Charmander was not your starting Pokemon, you will not find Suicune in the game. If you select another starting Pokemon, you will be able to find either of the other two legendary dogs. Start a new game file, if necessary, and choose Charmander as the starting Pokemon.
Complete the game's main storyline, defeating the Elite Four. Afterward, Suicune will wander through the Kanto region. It changes locations each time you enter a new area or a building. Suicune appears at Level 50.
Place a Pokemon between Levels 49 and 50 as the first Pokemon in your party. Use a Max Repel, which will prevent you from encountering Pokemon lower than Levels 49 or 50 for 250 steps. Continue to use Max Repels each time one expires.
Roam the grasses of a particular area in the Kanto region, trying to enter into as many random encounters as possible. If after several encounters, you do not find Suicune, move to a new area and repeat Steps 3 and 4 to find Suicune.
Select a Pokemon for battle that knows the moves "Block" or "Mean Look," which prevent Suicune from escaping battle when you find it. Pokemon that may know these moves include Zubat, Jynx, Gengar, Duskull, Murkrow, Umbreon and Gastly, among others. Use Fire-type attacks to weaken Suicune. Use an Ultra Ball to capture it.
Save your game in "FireRed" or "LeafGreen" and turn off the system. Insert "Sapphire" into a second Game Boy Advance system. Connect the two systems using a Game Boy Advance link cable. Enlist a friend's assistance for the second system. Both players can turn on the systems and travel to the nearest Pokemon Center to initiate trade.
Speak to the Cable Club representative to start the trade process. Select Suicune to trade to "Sapphire." Confirm the trade. Save both games and turn off the systems.