Some people will tell you that a puppy needs to be four to four and a half months old before you start training him.
Nonsense! Puppies begin learning the moment they are born, and they don't put that learning "on hold" when you adopt them at six weeks old.
It is obvious that if the puppy is learning (and he is), then you should be teaching.
Puppies, like all baby creatures, learn through play.
Baby wolves learn to sneak up on and pounce on their litter mates so that they can successfully hunt for food when they are grown; but when they are babies, it is all just a game.
The same thing is true of puppies - everything is a game, and every game is a learning experience.
Play with your puppy, but teach him at the same time.
For example, the first thing that a puppy needs to learn is that you are the alpha dog.
You teach this to the puppy by rolling him over on his back.
This isn't a rough game.
He just play a tug of war game or whatever and then roll the puppy onto his back.
You teach a puppy not to nip by playing with him and chastising him with a firm "NO" when he does nip and lavishing praise on him when he doesn't.
The same thing is true of house training.
You give a firm "NO" when he makes a mistake, but pile praise on his little head when he gets it right.
You can train the puppy early to not bark incessantly.
When you play with him and he barks, don't laugh because it is cute.
Catch his muzzle between your thumb and first finger and say "NO" firmly while giving a closing motion with your other hand.
It won't take long for him to get the idea that just barking for fun isn't acceptable.