How do you get the exp share in Pokemon Black and White?

How do you get the exp share in Pokemon Black and White?
You get it in Castelia City.
Go to the Battle Company building and go to the 55th floor.
You get it as a reward for beating the Janitor, I think his name is Geoff.
There's a few people you battle there.

The Lucky Egg is another good way to train up pokeon quicker. You get the lucky egg from Professor Juniper after entering that electric cave (Chargestone cave).