"To break up a dog fight requires 2 people. Each person grabs the back feet of one of the dogs. The dog back feet are then picked up like a wheelbarrow. With the legs up, both dogs are then pulled apart.
Once the dog fight is broken up and the dogs pulled apart it is critical that the people do not release the dogs or the dog fight will begin again. The two people need to start turning in a circle, or slowly swinging the dogs in a circle while they back away from the other dog. This stops the dog from curling and coming back and biting the person holding their legs.
By circling the dog has to sidestep with its front feet or it will fall on its chin. As long as you slowly continue to back and circle, the dog cannot do any damage to you. To insure that the fight will not begin all over again when you release the dogs, one of the dogs needs to be dragged into an enclosure (i.e. a kennel, the garage, another room) before the dog is released. If you do not do this, the dogs will often charge back and start fighting again or if you release the dog to quickly the dog will turn and attack the person who had his feet.
Dog fights are a very dangerous thing to try and break up alone. You should never rush in and try and grab the dogs to pull them apart. They are in high "fight drive" and are not thinking clearly when fighting. If someone grabs them they will bite without even thinking about who or what they are biting. This is how your loving pet can dog bite the living crap out of you in about a second and a half.
In reality it probably doesnt even know its biting you. I compare it to a bar fight. If a person comes up behind 2 guys fighting and just reaches out and grabs the shoulder of one of the combatants most of the time the fighter is going to turn and throw a punch without even looking at who or what he is hitting. This is because his adrenaline in pumping and he is in "fight drive".
The worst case scenario is that you are alone when a serious fight breaks out. There are a couple things that you must keep in mind:
Keep your cool you have a job to do.
Do not waste time screaming at the dogs. It hardly ever works.
Your goal is still the same; you must break up the fight without getting hurt.
Go get a leash (allow the fight to continue while you do this).
Dogs are almost always locked onto one another. Walk up and loop the leash around the back loin of the dog by either threading the leash through the handle or use the clip. I prefer the thread method.
Now slowly back away and drag the dog to a fence or to an object that you can tie the leash to. By doing this, you effectively create an anchor for one of the dogs.
Then walk around and grab the back legs of the second dog and drag it away from the dog that is tied up. Remember to turn and circle as they release.
Drag the dog into a dog pen or another room before you release the back legs.
Go back and take the dog off the fence and put him or her into a dog kennel.
Sit down and have a stiff drink (or two).
People talk about using cattle prods or shock collars to break up 2 pets that fight. I can tell you that many times this is not going to work. The electric cattle prod or electric collar will only put the dogs into higher fight drive. When they are shocked they will turn and bite the prod, or when they are shocked they will think the other dog is causing the pain and they will fight harder. An electric collar is best used in conditioning training, but not during an actual dogfight.