Inhibiting the Force of Bites
The first step is to stop your puppy from hurting people: to teach him to inhibit the force of his play-bites. Physical punishments are certainly not called for. But it is essential to let your puppy know that bites can hurt. A simple "Ouch!" is usually sufficient.
When the puppy backs off, take a short time-out to "lick your wounds," instruct your pup to come, sit, and lie down to apologize and make up and then, resume playing.
The next step is to eliminate bite pressure entirely, even though the "bites" no longer hurt. While your puppy is chewing his human chew toy, wait for a bite that is harder than the rest and respond as if it really hurt, even though it didn't:
"Ouch, you worm! Gently! That really hurt me, you bully!" Your puppy begins to think, "Good Heavens! These humans are soooooo sensitive. I'll have to be really careful when mouthing their delicate skin."
And that's precisely what you want your pup to think: that he needs to be extremely careful and gentle when playing with people.
DECREASING THE FREQUENCY OF MOUTHING
Once your puppy has been taught to mouth gently, it is time to reduce the frequency of mouthing. Your pup must learn that mouthing is okay, but he must stop when requested. Why? Because it is inconvenient to drink a cup of tea or to answer the telephone with fifty pounds of wriggling pup dangling from your wrist. That's why.
It is better to first teach "Off" using food as both a distraction and a reward. The deal is this: once I say "Off," if you don't touch the food treat in my hand for just one second, I'll say, "Take it" and you can have it.
Once your pup has mastered this simple task, up the ante to two or three seconds of non-contact, and then to five, eight, twelve, twenty, and so on. Count out the seconds and praise the dog with each second: "Good dog one, good dog two, good dog three," and so forth. If the pup touches the treat before you are ready to give it, simply start the count from zero again.
Your pup quickly learns that once you say "Off," he can not have the treat until he has not touched it, for, say, eight seconds, so the quickest way to get the treat is not to touch it for the first eight seconds. In addition, regular hand-feeding during this exercise encourages your pup's soft mouth.