Instructions
Obtain eight gym badges by defeating the eight Johto gym leaders. Go to the Indigo Plateau of Kanto, where you will find the Pokemon League. Heal your party at the Pokemon Center inside. Defeat the Elite Four and the Pokemon League Champion.
Catch a Pokemon with the "modest" nature and make it your lead Pokemon. Go to any one of routes 7, 8, 13, 14, 33, 36 and 45. When you're there, use repels, walk in the long grass and change routes frequently. Eventually, your partner Pokemon will find a Shiny Leaf. Talk to Ethan or Lyra in New Bark Town after you have found five Shiny Leaves.
Choose three Pokemon to participate in the Pokeathlon Dome with you. You and your Pokemon will take part in a random Pokeathlon event. Outdo the records for all 10 Pokeathlon events. If you want to beat the two records for Hurdle Dash, you must attain 101 points.
Go to the Battle Frontier by traveling north on Route 40. Walk to the Battle Tower, which is located in the very northern part of the Battle Frontier. Decide if you want to battle with two or one Pokemon. Use your battling experience to defeat as many trainers as you can in a row. You will get a star once you beat 100 trainers without stopping.
Finish your National Pokedex by catching every non-Event Pokemon. Once you have completed the National Pokedex, you will have captured 484 different Pokemon. You don't need to capture Pokemon like Mew, Celebi and Jirachi, because players can only obtain these rare Pokemon at special events.