Look in the coop discussion section of these forums, and also click the "coops" button at the top menu and you'll get loads of great ideas on making your chickens home safe, comfortable, and easy to maintain.
It is especially important to keep it really secure so predators can't get in, especially at night.
Oh, and your question about their aggressiveness, chickens are naturally "chicken", they are scared- it is their survival instinct, so it takes a while to win their confidence and get them used to having you near them. I pick mine up and massage their legs every day, and after a while they get used to me.
Edited by Gargoyle - 3/19/12 at 5:00pm