Follow the instructions provided here.
You must hold the 'A' button to walk slowly. Running will scare the Pokémon away, so sneak up on it carefully.
Visit the helpful man in Devon Corp. He will trade your Pokémon and then trade it right back to trigger its evolution.
Obtain the Mega Ring from your PC at home, give a Mega Stone to a compatible Pokémon, and in battle, press 'Fight', then 'Start', and choose your move.
Acquire the Z-Ring from your father, give a Z-Crystal to a compatible Pokémon, and in battle, press 'Fight', then 'Start', and pick your move.
Please refer to the "Wild Encounters" document included in the original game download to locate specific Pokémon.
Go to the second floor of any Pokémon Center and talk to the man on the left. Ensure you save before using a code and check for correct typing.
After delivering the letter to Steven for Mr. Stone, return to Mr. Stone in Devon Corp to receive the Exp. Share.
Increase your chances of encountering a shiny Pokémon by creating an encounter 'chain' using the DexNav. Each successful encounter in the chain boosts the odds.
You must capture Hoopa first, which is a roaming encounter after the 5th badge. Once a day, Hoopa may open a portal while you're adventuring, summoning Ultra Beasts and other legendaries.