Is there anything I need to know before playing?

SuperZambezi said:
I know how to play Pokemon, but I'm asking if there is anything I need to know from the first Black and White. Mainly story wise, but I'll take any significant details.
There's very little story changes. But major details. Most of the game aspects carry over.

Alder was the champion in the first games, but now a trainer.
Iris takes over Alder of being the new champion. She used to be the Opelucid Gym Leader in Pokémon White Version.
In the first games, N was one of the antagonists. But now, N is missing.
You will fight the same Gym Leaders, of course, but a few changes in Gym Leaders. You will no longer face the Striaton City Gym Leaders (Chili, Cress, and Cilan), Nacrene City Gym Leader Lenora, and Iccirus City Gym Leader Brycen.
Cheren takes over Lenora, and new Gym Leaders Roxie and Marlon will face you.
There is also the Pokémon World Tournament in Driftveil City.

That's pretty much the significant details you need to know.