Here's what I suggest:
Puppies tend to nip a lot in play, and their pointy little milk teeth can easily puncture skin. Aside from the pain factor, a nipping puppy that does not learn to curb this behavior will often grow into a dog that uses his mouth for rough play. While the intention is benign, the damage can be great, and a dog bite, is a dog bite according to the law. By starting young, you can easily teach your puppy or young adult that mouthing is just not acceptable.
Yelp and Shun
The most effective method is the "Yelp and Shun" method.
Try "yelping" in a loud high-pitched voice when he bites. As soon as he lets go, turn away from him, and refuse to play any longer. This mimics the behaviour that his pack-mates would use when he gets out of line. Before long, your puppy will learn that using his mouth on his people cause his people to turn away from him.
Other methods that may work with your dog are:
Trade
Trade me that arm for this toy, and you'll recieve plenty of praise when your chewing is redirected to an appropriate outlet.
Instant Muzzle
When your puppy grabs your hand, flip it around on him and wrap it around his muzzle, holding his mouth closed for a few seconds. This is not a pleasant experience, and many dogs often get the hint fairly quickly.
Play biting can evolve into a serious problem, so it is best to find out which method works, and employ it to teach your dog appropriate play.
