Things You'll Need
Instructions
Head north on Route 43 from Mahogany Town in the Johto region. Have a Pokemon who can use "Surf" to float out into the middle of the lake. Find the red Gyarados, move next to it and press the "A" button to start a battle.
Use a Pokemon with Electric- and Rock-type moves to do the most damage. The Gyarados is level 30, so use a Pokemon strong enough to withstand its attacks. To capture Gyarados, get the health bar into the red before throwing a Great Ball at it. Status effects, such as sleep and paralysis, will make the Gyarados easier to catch. To knock it out, just keep attacking until Gyarados' health bar is empty. Once the battle is over, it will drop a Red Scale.
Go to CherryGrove City (a Pokemon with the "Fly" ability will make it faster). Travel northeast on Route 30 to Mr. Pokemon's house. Talk to him, and he'll offer the Experience Share for your Red Scale.