When dealing with a nippy or mouthy puppy, it is important to recognize WHY your puppy is nipping in the first place. Puppies explore the world with their mouths, just like human babies. They want to put their mouth on anything and everything in reach. They also use their mouths to engage in playtime. If your puppy is nipping and biting you because they want to play, and you then proceed to play with them to get them to stop, you are actually reinforcing them biting you! Often times, we don't realize we are reinforcing bad habits. So here are a few ways to stop the biting without reinforcing it:
When your puppy bites you, do not start flailing your arms, hands, feet, or legs around trying to get them off. This actually engages them in playtime and they see it as fun. Once your puppy puts his teeth on you, stop all movement. Freeze your body and do not even look at him. If you aren't engaging him, then biting isn't getting him the playtime he wants and he will stop. If you can't stand the biting and wait for him to simply let go, then move on to step 2.
2. Leave the Room
Just as in step 1, you do not want to flail your limbs about trying to get your puppy off of you. Calmly stand up, and leave the room. Shut the door behind you if you need to so your puppy can't follow. Chances are he will follow you, wondering why his human is walking away when all he wanted was to play. Once the biting stops, then you can proceed play.
Another option you have is redirecting your puppy's biting. Give him an object he should be chewing on instead of your hand or foot. Give him his favorite bone, stuffed animal, or chew toy.
Puppies learn from their litter-mates how hard the they can play with each other. This is called bite inhibition. A puppy's bite inhibition with other dogs is different than bite-inhibition with a human. Puppies teach each other this bite inhibition by screaming and squealing when their littermate bites them too hard. To have your puppy stop biting you, simply imitate their litter-mates. Make a high pitched screaming sound. Your puppy will look at you, probably a bit confused, and then proceed to do something else.
5. Use a Chewing Deterrent
Chewing deterrents are any spray similar to bitter apple spray. They work equivalent to ointment that you put on a kids nails to get them to stop biting their nails. Chewing deterrents do not work on every dog, and you may have tottery different ones before it works. These are not to be used as every day solutions; a chewing deterrent is merely a management tool and must be coupled with one of the above methods to successfully eliminate a biting/nipping problem. To use a chewing deterrent, simply apply to your hands, clothes, feet, etc. without the puppy knowing. When the puppy goes to bite you, it will taste yucky to them, deterring them from continuing to bite you. This taste must be consistent in order to work. If they go to bite you sometimes and it doesn't taste bad, they may continue to try to bite. Again, this is only a management tool, not a be all end all to solve chewing and biting problems.