Puppies have painfully sharp baby teeth, but the jaws are under-developed, enabling pups to play-bite safely.  When a puppy bites another pup too hard, he gets blasted with a piercing "yelp" which instantly makes him back off.  Then something interesting happens – they start to play again, but now the biting is softer.  This is how puppies learn to inhibit the force of their biting before they become adults with powerful and dangerous jaws.  It is similarly essential for puppies to learn to inhibit their biting with humans. 

Many new puppy owners are instructed to discourage all play biting, this can be very dangerous.  If not allowed to play-bite, the puppy (just taken away from his littermates) will never have the chance to learn to control the power of his jaws.  The pup must first be taught to bite softly, then be taught not to bite at all. 

Allow your new puppy to play-bite by letting your pup chew softly on your hand.  When he bites down a little harder than normal, "yelp" sharply and loudly.  Don’t pull your hand away:  let the puppy back off (pulling your hand away will only encourage him to playfully leap towards it).  The puppy will probably lick your hand as an appeasement gesture, let him.  Then allow the play to resume, but this time, with a softer bite.  If the play gets a little rougher, "yelp" again, thus further decreasing the force of his bite.  Keep repeating this sequence.  And persevere. 

After a few days, puppy biting becomes puppy mouthing; in fact, you have fooled the puppy into thinking he must not exert any pressure while mouthing because your skin is so sensitive.  Now you can teach him commands, such as "don’t touch" or "off", to stop the mouthing altogether. 

A dog that has been taught to inhibit the force of its bite is a SAFE dog