If he is very food oriented, at least for treats. When you have something you want him to do use a treat, always. It truly does not matter if a dog sits for you because he loves you, is afraid of you, or wants a cookie. What you want is the result, and if a treat thrown in a crate gets him in the crate, I would do it. He is still learning, and eventually will do these things because you tell him. He will remember only that doing what he is told is fun and a good thing. Lots of praise too.Â
When he is being unruly, put him in a crate. Before you do it, tell him in a low slow voice "I do not like it when you do this", pick up his favorite treat or toy and throw it in his crate. Do not stare him in the eyes, look at the ground, a star is an invitation to fight. Then ignore him while he is in the crate and when he gets out for 10 minutes. Then ask him to do something, down, sit, whatever, give him another small treat and pet him and tell him "this is how I like you". Work on basic house routine. If he comes to you and wants you to pet him - say "If you want me to pet you you will have to sit" If he does, lots of wonderful petting, and Good Dog. If he doesn't get up from your chair and walk away. He will figure out very quickly that he must do what you ask to get attention. No big attention, unless he does something for you first. Going out the door, you go first, him last. Work on stay, it's very important. Start with three seconds, then build up. Another good way to exert control is down. Get him to lay down next to you. You can even sit on the floor with him, the down should be built up from three minutes to 30 minutes over a couple of weeks. You can pet him, even give him treats, he just has to remain down. Sometimes a leash is necessary. If he misbehaves, "I don't like...." and in the crate.
If you are having problems with jumping, turn you back to him and fold your arms, this also works well if he is grabbing your hand. He is just asking for attention, it is not agression, just dumb puppy stuff. Again turn you back fold you arms and walk away. After a few seconds go up to him and ask him to sit. Walk in to him, so he has no choice but to sit. Then lots of petting, he probably loves to have his ears rubbed best, just a few seconds of it, then "That's enough, go lay down" Do as little as you can to excite him. No running in the house. If he likes to retrieve, do it outside in a controlled condition. Never chase him or let him chase you or anyone else.  Lots of chew toys is a good idea, empty milk jugs, uncooked beef bones, whatever.
You should probably have him on a prong collar as well. Walking with him will also help establish you as the leader of the pack (that is what all this is about)! Do not let him pull against the prong collar, in fact never let him pull. Newfs were bred to pull and when you let him he is the happiest dog in the world, he is doing what comes naturally. Short jerks on the prong, if he won't stop, you stop. Tell him to walk with you, and do not take another step until he comes to your side. Again treats, and show him where you want him to be, right next to you.
the above is what a breeder friend of mine does, i have used these methods plus other methods, your first rule is to go to several classes, around other dogs and distractions and work on ATTENTION training, without his attention, you wont have his respect.
it all comes down to working thru his problems in public areas around distractions the correct way, mine go thru several obedience classes thru their whole lifetime.
I do not use any of the new collars or halters, instead i work on their eye contact and attention with lots of about turns, treats, and praise, going to the right trainer and classes makes all the difference in the world.
