Territorial dog aggression usually is experienced by protection or herding based breeds. This is the tried and true scenario in which your dog barks or growls anytime they catch a glimpse of someone coming to the door or through your yard. This reaction is reinforced when the dog succeeds in making the person or other animal leave immediately by showing their aggressive nature.
A good way to combat this is to plan ahead with someone the dog is not familiar with. Let them walk through the yard or up to the door and once your dog begins barking or lunging have them toss him one of his favorite treats. As the dog takes a break to quietly munch on the snack the person should praise them and walk away. This lets your dog know that in order to get the result they are looking for it is better to be calm and not aggressive.
If you think your dog is showing signs of aggression, sign up for a free in home evaluation with an All Star Dog Trainer!