Puppies play with each other by nipping and biting and slapping each other with their paws.  It is a very natural thing to do.  It can be very confusing to a pup to be scolded for playing the only way he knows how.  And then turn around and encourage him to play again.

With a young pup you may want to pursue "natural" ways of teaching him not to nip as his mother would if he were in the 'pack'.
When he bites you - YELP ( or say ouch ) - in a moderatly loud high pitched tone of voice much as litter mate would when hurt.  This may take several times for him to get the idea. You may also couple it with pulling your hand back in an exaggerated motion as another pup would retreat from being hurt.  Do not yelp so loud as to frighten the pup.  Immediatly give the pup a "proper" toy to bite. (if your pup is teething you may want to give him a dampened then frozen washcloth to chew ) Puppies have short attention spans. It may take your pup a few times to a few weeks to get the idea that biting hurts and is not allowed. It is important to be consistant with any training.  Everyone on the family and visitors alike should react the same way to being nipped.

You may consider doing as the mother dog would and grab him by the scruff on the neck and give him a gentle but authoratative shake ( do not lift the pup off the ground to do this ).  This is what his mother would have done to teach him and he may remember that. As the pup grows if he is still nipping or playing to rough you may want to add the motion of putting your hand over his muzzle firmly immediatly after you yelp and tell him 'no bite' ( in a growling tone of voice to again simulate his mother ). Then give him his proper toy for chewing and biting. Be sure to praise him for chewing on the proper toy.  All training sessions should end on a good note.

As part of the tools used in obedience training you should have a chain collar.  (note the collar goes on so it will loosen immediatly when the dog is on your left)  put your leash and collar on your pup.  Set up a situation in which he is likely to nip and correct him with a slight jerk on the collar. ( a jerk on the leash followed by an immediate release - do not choke your pup).  Couple this with the 'no' command and a 'no bite'.

Your dog needs to understand his position in the pack. Your family is part of the pack to him.  Children may be considered littermates. You need to be aplha dog. This position needs to be established while the pup is young as it is much more difficult to assert your self as the leader of the pack after your dog has gotten used to a feeling of higher stature. You dogs thoughts on the way things should be done may not correspond with yours.  A dog that thinks he is superior may try to enforce his way with aggression to control his pack.

Coating your hands with bitter apple or vinegar may help a young pup to decide hands taste bad during play nipping behavior.

Feeding your pup his treats or part of his meal by hand while telling him he is good coupled with petting him and rubbing him may help him learn that hands are for being petted not for biting.  Holding a dog biscuit in your hand so he has to work at getting it with his tounge - not his teeth - may help him learn that hands are not for biting. If he trys to use his teeth to get at the biscuit withdrawl the offer for a little bit.

Another school of thought is to totally ignore your pup when he does any unacceptable behavior.  Purposely ignore him for 5 minutes, walk away do not speak to him or anything. He wants your acceptance and approval.  Dogs are social animals they need interaction.

Divert your pups attention from thinking of parts of your body are chew toys  by offering proper toys.  Initiate a game of fetch but discourage tug of war games and wrestling until your pup has learned you are not a chew toy or littermate to be played roughly with.

If your pup is very headstrong and dominate you may need to pursue more negative reinforcement. A loud or startling noise can distract your pup from his objectionable behavior.  A rolled up newspaper slapped against your hand or a table.  A pop can with some pennies in it to shake. Coupled with a stern 'no' or 'no bite' can get the idea across to some headstrong types. Warning signs your pup is considering biting include growling and/or showing of teeth, a hard glassy-eyes stare, stiffening of body posture with ears perked and legs stiff or a warning bite ( a quick snap in your direction ). Do not let a wagging tail fool you.  A dogs eyes are more informative than the tail. If a dogs pupils are small he is not afraid - he may be angry. If his eyes a wide and the pupils large his is scared.  He may bite out of fear.

Most puppies go through stages of biting and mouthing. It is normal behavior if he was still with his littermates.  In the litter pups use biting and mouthing as play and to establish dominance over littermates. However, with a human 'pack' biting and mouthing can be annoying behavior - especially with those sharp puppy teeth.

Obedience training helps give a pup a sense of accomplishment and helps with his bonding to and respecting you.  8 weeks of age is not to young to start learning some basics if you keep lessons short and gentle.  Your pups learning some simple things such as sit can help with his learning other things.