Pokemon X and Y have been released, and one feature that is drawing a lot of attention is Mega Evolution.

Since the release of X and Y, a few more updates have become available about the Mega Evolution.

Firstly, only one Mega Evolution can occur in a single battle, so choose wisely.

Secondly, the locations of all the Mega Stones known so far have been updated on Serebii. They are as follows:

Venusaurite: Professor Sycamore's laboratory if chosen as a starter. Vernal Avenue Stone Emporium if not chosen as a starter.
Charizardite: Professor Sycamore's laboratory is chosen as a starter. Vernal Avenue Stone Emporium if not chosen as a starter.
Blastoisite: Professor Sycamore's laboratory is chosen as a starter. Vernal Avenue Stone Emporium if not chosen as a starter.
Alakazite: Postgame. Reflecting Cave B3F.
Gengarite: Laverre City. Given to you.
Kangaskhanite: Postgame. Glittering Cave.
Pinsirite: Postgame, Pokemon X only. Satalune Forest.
Gyaradosite: Postgame. Couriway Town.
Aerodactylite: Ambrette Town. Given to you.
Mewtwoite X or Y: Pokemon Village Unknown Dungeon. Type changes depending on game.
Ampharosite: Azure Bay. Given to you.
Scizorite: Postgame. Frozen Cavern.
Heracrossite: Postgame, Pokemon Y only. Santalune Forest.
Houndoomite: Postgame, Pokemon Y only. Route 16.
Tyranitarite: Pokemon X only. Cyllage Gym.
Blazikenite: Torchic Event
Gardevoirite: Southern Boulevard, Café. Also held by traded Ralts in Lumiose City.
Mawilite: Shabboneau Castle.
Aggronite: Pokemon Y only. Cyllage Gym.
Medichamite: Postgame. Laverre City.
Manectricite: Postgame, Pokemon X only. Route 16.
Banetteite: Postgame. Cave of Emptiness.
Absolite: Postgame. Kiloude City. Given to you.
Garchompite: Postgame. Victory Road.
Lucarioite: Held by gifted Lucario.
Abomasnowite: Frozen Cavern. Given to you.

One thing Pokemon X and Y fans have noticed is that typically, only one Mega Stone is available for each type per game. This means that for fans to truly take advantage of Mega Evolution, they would have to strategize trading with others to make the most of it. It would be unwise, for example, for one person to trade their single Mega Stone for another.