Let's talk stones
Locations
I wish these were more like shinies, in that, the only way to obtain one is to encounter a pokemon holding the stone, pre-evo or not, and then some sort of animation or sound to signify the item's presence I think that would make these pokemon more rare and special.
From the info we have, it's hard to tell if the stones are set in stationary places since it says,
"Some of the many Mega Stones seem to be hidden in secret places in the Kalos region. Finding every one of them will be one of the challenges awaiting you in Pokémon X and Pokémon Y!"
I hope they are not like hidden items that are easily discovered by using a simple google search. This could be interpreted several ways though, stationary placement may not be the case. It could be the case that the items are hidden in randomly generated areas. I hope they are able to in a way make the hunt similar in difficulty as encountering Feebas in RSE. That way the trainer might have to look in a particular areas for a stone, but never know the exact location with each runthrough of the game. And, I tell you, I love Milotic, the hunt made me cherish it even more! (except my last run through, in which I encountered one on my first cast of the fishing pole.)
Other requirements
"Only certain Pokémon, under certain conditions, can achieve Mega Evolution. One of those conditions is a special item called a Mega Stone...Other things are needed for Mega Evolution to succeed, and those secrets will be explained later!"
Wondering what other conditions may be needed, I am thinking that it hints to something unique to each Pokemon, not something that is not secret worthy like perfect EV training. For instance, Ampharos learning a specific dragon move or Kangaskan obtaining max happiness. Erm, I can't think of anything that creative at the moment, but you get the gist.
What conditions other than a stone do you think will be required?
