Puppies use their mouth to feel their environment. You need to teach your puppy what to and what not to chew on. When a puppy is chewing on something he/she should not be, give a FIRM NO while tapping on the nose. After this give the puppy something it IS allowed to chew on. Praise the puppy, teaching the puppy this is something ok to chew. When puppies chew or nip on hands and feet, use the same technique. Make a "OUCH" sound, than say NO with a firm voice while giving a tap on the nose. Give the dog something it is allowed to chew on and praise your puppy. You are your puppy's’ teacher, If you do not start teaching your puppy at a young age what is and is NOT acceptable, Your puppy WILL think that it is ok to do whatever he/she was doing.