Like Ash, I can't tell you exactly how the trading system will work this generation. However, it usually involved visiting one of the assistants at the Pokémon Center. Normally when trading with someone, and I doubt this will change, you're allowed to check out the Pokémon the other player has and they can see yours as well. You're able to see the levels, stats, moves, and other details of the Pokémon from the other player. Before the trade happens, both sides have to confirm it and you'll also be able to see exactly what Pokémon they're trading you and vice versa. This way, no one ends up getting the short end of the stick. You know exactly what you're giving up and you know exactly what you're getting as is the other player on the other end.
With X and Y, you won't be able to trade back and forth with older generation games. You will only be able to store Pokémon in the PokéBank using Black, White, Black 2, White 2, X, and Y. And you can transfer Pokémon from the 5th Gen games over into X and Y using the Transporter. If you want to learn more about this, head on over to this thread
here.
Other than that, I don't think much else is left to be said. I hope this answers all of your questions you had.