Fear

• Most aggressive dogs became that way though fear. They were treated unfairly and learned that aggression gave them a measure of control in their surroundings. Teaching one of these dogs to trust you and be confident in his surroundings requires time and a lot of patience. You must prove to the dog that he can depend on you consistently to be fair and that you are looking out for him.
  
  To begin, assess the dog for the triggers of his aggression. Does he hate the mailman, the gardener, anyone who touches his food, other dogs, maybe all of these things? Now that you know what triggers an outburst of aggression, do your best to avoid these situations until you can instill some trust in him. Every event that scares him sets you back a bit.
  
  

Training

• Start with basic obedience training, commands such as "sit," "stay" and "down." With any dog but especially aggressive dogs, use positive reinforcement training, offering him a reward for performing the desired behavior. Negative reinforcement training, a punishment for a wrong behavior, continues to reinforce there is something for the dog to fear.
  
  Once basic obedience has been taught, move to slowly introducing the stimuli that triggers the dog under a controlled environment. For example, if the dog becomes aggressive with other dogs, introduce him to another dog in the following way.
  
  Have a friend with a well-mannered dog help you. Have both dogs on leashes and take them to an area where you can keep a fair amount of distance between them. Have both dogs sit and praise them for focusing on you. Slowly shorten the distance between the dogs all the while keeping the focus on you and your dog listening to basic commands. The dog will soon realize that he is all right and the other dog is not trying to hurt him. This must be repeated many times with different dogs to truly break the old habit. Use this basic technique to slowly introduce other triggers.