Consequence drives behavior... even with puppy biting!
Puppies use their mouths a lot to explore their world and it can be very painful for those at the receiving end. This behavior is a normal part of development - they need to mouth and chew as much as a human infant needs to teethe. At the same time, puppies must learn to respect human skin and clothing and understand where the line is so that they don't develop a joy of "mouthiness." They can grow into this behavior rather than out of it! If things start to get out of control, it is better to separate the puppy from his victim rather than try to correct him, which he might see as an invitation to keep biting!
Got a Chewer? A Thief? An Elusive Runaway?
Set up your puppy's environment so that he doesn't have access to the things he shouldn't have. Be sure not to get confrontational about objects your puppy may have that you don't want him to have. He's just exploring his world and is bound to find just about everything interesting. In dog culture, if he has it in his personal space, it's his. Instead of getting mad at him, chasing him or yelling at him, be ready to trade him for appropriate objects - and take responsibility for keeping inappropriate items out of his reach. Do not try to pull something away from him - he will just hold on tighter next time. Trade, trade, trade! Run away to get him interested in chasing you, find something he might like instead and trade.
My prescription is two-fold: Prevention and Training
1. Lots of off-leash, aerobic exercise
2. Lots of interactions with appropriate dogs of all ages. Dogs are best at doling out effective discipline and an adult dog with good communication skills can be invaluable in the learning process. In doggie culture, when one dog has broken a rule of engagement, there is an immediate consequence which results in end of play.
3. Confining the dog at times when mouthiness can be predicted
4. Redirecting to appropriate items such as food-stuffed toys, bully sticks or tracheas, soft toys, etc. The ultimate chew toy: raw meaty bones (like knuckle bones - not marrow bones). Gnaw, gnaw, gnaw!
5. Fitting the puppy to a harness and attaching a drag line to it ("remote control"). This set-up allows you to step on the line so you can interrupt behaviors such as chasing and jumping.
6. Give that puppy mouth something to do while handling. Offer him something to lick in one hand while you wipe his feet, put on his collar or harness or do other handling. Put a food stuffed toy under your foot to keep that mouth busy if you need two hands.
While puppy is on tether, start engaging him with a toy or just with petting. The instant he starts to cross the line (teeth on you), say "oops!" and withdraw all attention for 3-5 seconds. As your puppy gets good at this (and as long as your timing is good), you will be able to increase the level of animation and your puppy will be able to maintain his bite inhibition. Practice off tether. TIPS: keep your pup's mouth busy with a toy or a chew while you are touching him. Set up tethers throughout your house so you have a place nearby to confine your puppy (always with supervision).
2. Impulse-Control Exercises
Exercises that help your dog learn how to control his emotions will help tremendously. Those include 1) food bowl exercise with food and toys, 2) door etiquette, 3) "soft mouth" exercises in taking treats, 4) settle, 5) tug with rules
3. Desensitization to movement
Teach your puppy to target your hand (if he's nippy with your hand, turn it into a fist or use something larger like a fly swatter or wooden spoon). A target-happy puppy is going to be easier to redirect to something else.
Here are good videos on how to address puppy nipping:
Lastly, don't despair! With consistency, prevention, training and time, your puppy will learn to be careful with his mouth. By 3-7 months, those sharp puppy teeth will be replaced by a full set of 42 adult teeth.