Leave it to The Pokemon Company to not make accessing the Pokemon Omega Ruby & Alpha Sapphire demo a straightforward affair. Instead of simply heading to the 3DS eShop, you'll have to redeem a special code that's being distributed by different outlets in each region. For North America, you'll receive the code on October 21 via the Pokemon Trainer Club Newsletter. In order to get the newsletter, you'll have to join the Pokemon Trainer Club before October 19.
So what can you expect in the demo? As Serebii reports, you'll be dropped into Mossdeep City with a starter Pokemon of your choosing — Grovyle, Combusken, or Marshtomp — set to Level 35. You'll also be able to obtain a new Mega Evolution that han't been revealed in previous materials, and once the final game is released, you'll be able to transfer it over along with a few other items. The Mega Evolution you find differs depending on the region — of the locations where the demo has already been released, Europe, South Korea, and Australia gets Mega Glalie, while Japan gets Mega Steelix.
Pokemon Omega Ruby & Alpha Sapphire come to 3DS on November 21.