An example is a pup that grabs at it's leash and owner, while getting ready for a walk. In the scenario don't reward the pup for grabbing and play biting with a walk. If your pup is very intense you may need to find a way to break this association of biting, with the leash and walks. Try getting the pup to hold a chew toy or look in to formal dog training. Now that you are not encouraging mouthing, you will start to find times when the dog would like to mouth but chooses not to.
Some good rewards are food and playing retrieve. .
To get the most benefit from playing retrieve your dog should learn to get it's retrieve toy on command. This way when your pup starts to get mouthy you can give it something else to do. It is much more effective to have your dog get it's toy, than for you to give the toy to the dog for mouthing. A somewhat similar approach is for you to leave the puppy. When the puppy is to mouthy, terminate the social interaction and ignore the dog.