Biting is normal puppy behavior.
Puppies will put absolutely everything into their mouths because they are curious and want to learn about new objects.
Dogs also play with each other through play-biting.
While there is nothing wrong with play-biting amongst dogs, it is crucial to teach them that biting humans is unacceptable conduct.
If your dog is biting you and/or others, it is best for everyone not to engage in rough play with him.
Also, do not play dominance games like tug-of-war with him.
How to Stop Your Dog from Biting

1. Do not jerk away.
   When your dog has his mouth on you, it is important NOT to jerk away.
   Jerking away will cause you to get scratched.
   More importantly, sudden and quick movements may make your dog think it is a fun game and reinforce his biting/mouthing behavior.
   At worst, quick movements may instigate your dog's prey drive and cause him to get aggressive.
   Instead, stay still and either give a "No" command or yelp as a puppy might do to his litter-mates when they are playing too rough.
   I use the yelp for puppies who are still learning and for accidental biting.
   
2. Redirect onto a toy.
   This technique is especially useful for an untrained dog.
   It lets the dog know that it is acceptable to bite on a toy but not acceptable to bite on humans.
   Yelping will startle your dog and cause him to release his mouth.
   Quickly follow that up by redirecting him onto a toy.
   You do not need to shove it in his mouth, just put it there for him to bite on.
   
3. Time-out.
   If your dog continues with his bad behavior after you have told him to stop, then say "Time-out" and remove him to a time-out area (a safe but boring room, e.
   g.
   laundry room).
   Nobody is to give your dog any attention during this time.
   Leave him in there for one or two minutes, then let him out.
   If he starts his biting behavior again, non-mark him ("No"), say "Time-out", and put him back in time-out.
   This time lengthen the duration to about 10-15 minutes.
   Be flexible and tailor the time-out duration according to your dog's temperament and behavior.
   Some trainers do not believe in long time outs while others may ignore their dogs for hours or even days.
   If your dog stops his biting behavior, make sure to praise him well and give him good treats.
   Keep this up and your dog will learn that certain behaviors get him rewards while others get him into a boring room with nothing to do.
   Do NOTuse a crate for timeouts because the crate should be a happy place where your dog feels comfortable going to for some peace and quiet, sleep, and eating.
   Do not use time-outs for training mistakes or lack of motivation.
   
4. Hand-feed your dog.
   Hand-feeding is a good way to teach your dog good bite inhibition.
   Hand-feed your dog some of his kibble every day, by giving it to him one-by-one.
   If he bites too hard when getting his food, do a sharp "ouch" or yelp and ignore him for a few seconds, then start hand-feeding him again.
   If he is taking food from you gently, praise him and keep the food coming.
   In this way he learns that biting hard can hurt humans, and when he does that, the food and attention stops.
   Hand-feeding also helps with bonding, establishing leadership, and preventing food aggression issues; so it is good to continue this practice throughout your dog's life.
   
5. Nothing in Life is Free (NILIF) program.
   The best way to establish yourself as leader is through the control of resources.
   Do not give anything to your dog (including food, toys, freedom, and affection) unless he does something for you first.
   For example, ask him for a "Sit" before you let him outside, or ask him for a "Down" before giving him any affection.
   
6. Obedience training.
   Try and do some obedience training sessions with your dog everyday.
   Enroll in a class or get a positive reinforcement, obedience book, and practice with him for short sessions (10-15 minutes) every day.
   This will help establish you as a leader, improve your bond with your dog, exercise your dog's mind, and give you good tools to help control him in the house.
   
7. Stop Furniture Biting.
   If your dog is biting on furniture or household objects, you can deter him from doing this by spraying Bitter Apple on them.
   
8. Crate your dog.
   When you are not around to supervise your dog, make sure to crate him or put him in a long-term enclosure.
   Leave him with some safe chew toys and food toys.
   Crating prevents him from practicing bad behaviors, including his object chewing behavior, when you are not home.