Ferrets are very playful, and one of their most common misbehaviors is nipping. Gentle nipping is nothing serious, but when the ferret begins biting too hard, it’s time to remind it to calm down. You can do this by firmly saying “no” and then pulling away your hand. Some ferrets will get the idea faster than others. If the behavior keeps up, then after saying "no" again, just walk away from the ferret. If these two warnings fail, it’s time to put your ferret back in its cage. Ferrets love to have fun, so seeing that it is missing a good time will more than likely be adequate punishment. The key here is consistency. Make sure that every time the ferret bites too hard you don’t overlook it. Make the consequences stick. Over time, most ferrets listen and respond to the word "no" and then stop all action.
http://happyferrets.com/
http://happyferrets.com/