You want to keep it in a moist environment, so keep it covered. You don't want to put it in a cold environment until ~24 hours after renneting, to make sure the cultures have done most of their work.
I fianlly got around to making the parmesan.
It was store bought skin milk, and definately reduced the amt of cheese I got, but it is in the press now.
A pretty easy make, I must say. It was fun.