Instructions
Rare Candies
Connect your Pokemon game to an Action Replay or GameShark device.
Input the code for infinite Rare Candies at the code screen. This code depends on the version of Pokemon you are playing, but can be found online at various sites such as SuperCheats or NeoSeeker.
Start the game and use the Rare Candies on your Pokemon. Each Rare Candy raises the level of your Pokemon by one. With infinite Rare Candies, you can raise your Pokemon's level to the maximum level within a matter of minutes.
Daycare Center
Drop your Pokemon off at the Daycare Center. Every Pokemon game has a Daycare Center. Check sites as Serebii to see where the location of the Daycare Center is in your particular version of the game.
Ride around on your bicycle for several minutes. Each step you take equates to one experience point for your Pokemon. After enough steps, depending on the level of your Pokemon, it will level-up by one. This takes longer if your Pokemon is already at a high level.
Travel back to the Daycare Center and ask for your Pokemon back. You will have to pay some money to receive it back, but it will be stronger than before.
EXP Share
Attach the EXP Share item to a Pokemon you want to level-up quickly.
Place your strongest Pokemon at the first slot of your party.
Battle and defeat other strong Pokemon either in the wild or by battling other trainers. Once you have defeated them, both Pokemon will split the experience points even though only the first Pokemon battled.