R.T. Bucher says:

Dog biting training needs to start when they are just a puppy. Puppies like to nip and bite when they are just learning to play. This behavior can become a problem if you rough house with your dog and allow it to show aggressive behavior.

If your dog is grown up and past the puppy stage and it has begun biting and nipping at visitors and displaying traits of aggressiveness, then you need to put a screeching halt to it. Depending on the breed of dog, the more chances they will bite. Canines become very loyal to the people who feed them and house them, it’s in their instincts. They feel they need to protect them, even from your friends. They see each new visitor into your yard or house as a viable threat. Which of course increases the chance of biting.

Growling or barking are habits that need to be broken, these can lead to bigger problems later on, in the dogs life> Such as biting. Dog biting training should implement some type of reward system. If your pup or dog does something like laying on the ground when visitors arrive, reward him. What if he barks or growls at new comers? You must start employing some alpha dog tricks. Remove him from the room and then tell him no and put your neck on top of his. This will tell him or her who is the boss in the house. You need to make sure the dog knows his place in your house. The more times you allow him to get away with bad behavior, the room for biting increases.