Dog Aggression Problems

There is nothing more disconcerting at a dog show or at any dog gathering than to have an encounter with an aggressive dog. Whether that dog is crated or not, it still can be a frightful experience for yourself, or for your dog, or for your children that may be accompanying you.
When dogs are crated and display aggression, leaping and lunging and shaking the whole crate, along with loud growling, snarling, and lunging, it is completely unacceptable behavior. Handlers will try to excuse this behavior by saying that "the dog is territorial" in nature. Sorry, there is NO EXCUSE for this behavior, and it can be trained out.
What is even worse is the aggressive dog that is loose. This is more than unacceptable, it can be criminal. The aggressive dog that bites or threatens to bite can be placed in quarantine or worse yet, put down.
Aggression can range from dog/dog aggression to dog/food aggression to dog/human aggression. Regardless, this is a problem that is best approached during the early puppy training stages. Trying to straighten out this sort of behavior later on can be a real difficult problem for the novice dog trainer.
As for dog/dog aggression, puppy kindergarten classes are super because they expose the puppy to strange dogs AND strange people. A puppy that is under six months of age is automatically a "submissive" dog and learns how to interact in dog language to other dogs at this stage of it's life. Lacking a puppy kindergarten class, the new owner should attempt to find other neighborhood dogs and/or a dog park. Allowing the puppy to be off leash when being introduced to other dogs is a good idea. If the puppy is off leash, you will not be sending "distress" signals down the leash to your dog, if you are nervous yourself about these encounters.
Dog food aggression problems also are best approached during early puppy training. Putting your hand into your puppy's food while it is eating, allowing ti to eat with other dogs in the household, teaching it to take treats nicely from your hand without lunging, all of these are behaviors best taught when the puppy is young and impressionable. Simply putting your hand into your puppy's dish, picking the dish up while it is eating, and adding treats to the dish while it is eating will soon teach it that it is acceptable for people to handle it's food dish. Setting the dish down in an area where other dogs are eating will teach the puppy how to deal with other dog's trying to eat it's food, for if it becomes too out of hand, the other dogs will teach it to behave. Don't worry about the puppy actually getting hurt by another dog, since nearly all adult dogs will not tolerate a puppy stealing from their dish, and they will teach it in "dog language" not to interfere. This is something your puppy needs to understand from the beginning.
Dog/people aggression, here again, is NOT a problem a novice trainer should deal with if it is occurring with an adult dog. However, if the puppy is under six months and is exhibiting dog/people aggression, this will often be simply a fear reaction. Fearfulness is best overcome by allowing the puppy to investigate the stranger on his own terms. Do not force the puppy to accept a stranger, rather ignore his behavior and allow him to approach the stranger in his own time.
First and foremost your puppy needs to learn to trust in you. Exposing him to everything you can think of from other dogs to loud noises to lots of people will gradually build up his trust in you and that is the best solution to avoiding other problems later on. There are training tips for all of these possibilities and more in the new manual DOGSHOWS101, a great training resource for novice puppy owners.