Try squealing like a puppy when he bites you. An adult dog might know that you are not a puppy and will ignore the sound, but a puppy isn't as smart and will feel sorry.

If that doesn't work, then don't react at all. Just stand there and let him bite (you might need thick clothes for those puppy teeth!). Some puppies will bite just to get a reaction out of you, so take the fun out of it by giving him no reaction.