Aggressive behavior in dogs does not necessarily indicate that those dogs are mean or bad by nature. As experts in aggression dog training can confirm, aggression is often a means of expression for insecurity and being afraid. And these are the facts that efficient obedience training is usually based on.
Knowing the exact root cause of aggressive behavior certainly plays an enormous role in the whole process. In this respect, aggressive behavior is often caused by lack of socialization with other dogs, with traumatic experiences that the aggressive dog has had either with other dogs, or with people, or when the dog has to change the environment he/she had got used to.
Punishing a dog for aggressive behavior is not a good option, but enrolling your dog to obedience classes can prove to be a great thing. Apart from that, you can try to make your dog feel comfortable in your home, with other dogs and with new people. At the same time, it is best to avoid any kind of new action when your dog is present. The idea is to help your dog get rid of fear, which is usually the main source of aggressive conduct. Remaining calm is also tremendously important.