Basic Puppy Training and Socialisation are important things to teach early, especially in a giant dog.
Newfoundland Dogs have been bred for centuries to work on their own initiative and a dog with this working history will not respond to any sort of harsh treatment. You will lose his trust completely if you try. They are what might be called a stubborn breed, given to going their own way if they do not see a reason not to. You must make yourself far more important to them than anything that they might wish to do.
Socialisation should begin as soon as you have your newfoundland puppy home. He cannot be walked in the streets, until he has had all his vaccinations, but he needs to experience outside. You can carry him up the road, let him meet people and see traffic and other dogs, though do not let him too close to another dog unless you are sure that dog has been vaccinated. You will not be able to carry a Newfoundland puppy for long, but you can push him in a pushchair or stroller. You might feel stupid, but it is for the dog's own good! He needs to know that outside is nothing to be scared about
Practice loose leash walking in your garden, or around your biggest room if necessary. Your Newfoundland puppy is possibly going to grow up and be heavier than you and the last thing you need is for him to pull you off your feet. This should not be too difficult with a Newfoundland puppy, because generally speaking they are not given to pulling. Although they are still sometimes used for cart work and cart showing, that is not what they were bred for. However, you really need to know that you are in control if he sees something he wants! This is part of training your puppy and needs to be started whilst the dog is still a reasonable size to handle!