Mega Venusaur has the ability Thick Fat, Mega Charizard has the ability Drought and Mega Blastoise has the ability Mega Launcher. You will need to obtain a bracelet called the Mega Ring that holds a mysterious stone called a Key Stone. The Trainer's Key Stone resonates with the Mega Stone held by his or her Pokémon.
There's also a Pokemon Bank, basically a PC box stored in the cloud. You can store and download your mons on your 3DS whenever or wherever. This is their idea for trading Pokémon from previous gens to X&Y. There's a Pokemon Transporter for the same function, and these are still in development. BUT there's an annual fee for the maintenance of your box.