By the time your pup is five months old, he must have a mouth as soft and reliable as a fourteen-year-old working Labrador Retriever: your puppy should never initiate mouthing unless requested; he should never exert any pressure when mouthing; and he should stop mouthing and calm down immediately upon request by any family member. Move the treat in a straight line from the puppy's eyeline up to the bridge of your nose.