In a wolf pack there is always a leader. Usually there is a male and female leader but not always. The rest of the pack settles into a pecking order and the leader runs the pack. In your pack (your family and your dog) there must be a leader. If you do not assert yourself as the leader your dog will. Especially dominant breeds such as German Shepherds, Rotties, Dobies and Pit bulls. Although most any breed can take over this role if allowed. If your dog takes over as the leader you will get behavior that is not acceptable in a home. Such as growling when you come near his food bowl or toys, or growling when you try to get him off the couch or the bed. They can also not allow certain people in the house, etc. This can lead to biting if people don't do what the dog wants.
Dogs have an unspoken language and they understand each other very well. We as people do not understand dog language and can get in trouble with a dominant dog. One of the truly important things is never stare at a dog. In dog language this is a challenge and a dog could attack. The best thing to do is stand sideways and avert your eyes. Looking at a dog and quickly looking away is a signal that you want everything to be calm. Also not facing a dog straight on is showing him you do not want to challenge him.
Watching a dog's tail can tell you a lot. Just because a dogs tail is waging that doesn't mean everything is ok. Dogs that are very aggressive will sometimes wage their tails but they are usually straight up. Dog's who are frightened may wage their tail but it is usually down or tucked under them. A happy dog usually has a kind of smile on his face his tail is level with his body and waging very big.
One of the best ways to become the leader of your pack is through dog obedience. The more training your dog gets the more he understands how to live in your world. Training should be with someone who uses the reward system. With this type of training your dog really enjoys himself and he learns to bond better with you. If you are using the old fashion jerk and pull method your dog will learn through fear, that doesn't bond him to you and it sure doesn't make him happy. When I am teaching a class one of the most rewarding things for me is to see a happy dog.
When you can lure him into a down start having him do this when you are relaxed at night and can sit with him. AT first give him little tiny rewards as long as he is in the down. Just keep them coming one at a time. As time goes by you can give him less and less. Remember the dog will tell you what is a high ranking reward by the way he wants it. If he doesn't want dog treats tonight try hot dogs or cheese, that will get his attention. The idea of this is to make him think down is a really neat place. You have to remember that down is the most submissive position a dog can be in and some dogs really fight this. If he gets up you just lure him back into the down. Never, Never get upset. Always remember your dog is learning and the more patient you are the quicker he will learn. After you get him to stay until you release him, start making the time longer and longer. Then start moving away from him a little at a time. When you accomplish this you will have pretty go control over your dog. It also starts establishing you as the leader. Another thing you can do is eat first then feed your dog. The leader always eats first, the rest of the pack waits until he is done then they can eat.
One of the reasons we have so many dog bites in this country is because the dog has become the leader and that is how they are trying to solve a situation. Of course we also have fear (which is a big one too) and teasing a dog through a fence or when the dog can't get to the person teasing him. When they get free they can attach.
If you and your dog get an understanding that makes him want to follow the rules of the house you will have many wonderful years with one of the greatest gifts that man has ever received. YOUR DOG.