Dogs need to chew to relieve stress and excess energy. In fact, puppy teething is a natural part of development. If your dog chews on something that is off-limits, say "no" or "eh" in a low voice. Then give your dog a safe chew toy. Praise him for good behavior. Remember to give your dog safe chew toys instead of old household items like old shoes, because that could encourage him to also chew on new shoes. You will also want to avoid rough play and games like "tug of war" as this will encourage aggressive behavior

http://pets.yahoo.com/pets/dogs/bt/biting_&_chewing