A random spilling of my experience on the subject. . .
The main thing is just to know your dog and the area you’re walking him. Unneutered males attract fights. Submissive dogs don’t usually get attacked. Dogs on leashes seem to have more aggression than dogs off leashes – I think they either feel vulnerable or protective. And some dogs just seem to attract it.
If I see a dog coming towards mine, I grab my dog way down at the end of the leash by the choke chain, stand in between them, and yell ‘no’ at the approaching dog.
If I assess the situation and think there’s no way the other dog will stop, I’ll unclip my dog so he can defend himself away from me. Or run. A lot of times I’ve seen what looks like aggression just turn into a playful chase when the dog is unclipped.
If they do get together with my dog on the leash, I’ll try to pull him off by it, and I think that this removal of him from the fight lets the other dog know he’s won and it can be over.
BUT, if they are together, I have used the “grab back legs” tactic. I’ll also grab not actually by the legs, but by hooking my hands into the soft spots in front of the haunches. To help ensure the dog won’t spin on you, you might give him a good spin (let the centrifugal force keep his head away), and even toss him away if need be. The tail works too, but it’s sometimes flicking around so much that its hard to grab.
Every dog fight is different, though, so it’s hard to use a general rule. Even this “grab the back legs” is not always easy if the dogs are spinning and lunging. And some dogs (like a pit) could still turn on you so you might just want to stay away.
I’ve seen a lot of dog fights, and in like 95% of the cases, no dog gets hurt, so it’s not a bad idea to just stay out of it unless it’s clear one dog is getting mauled. There is often a lot of teeth baring and growling, but rarely serious biting or clamping down. They’ll usually stop when one dog decides to back down or is put on his back.
Picking your dog up is BAD. A dog will still go after him and I know a guy who got his face bit up when he picked his dog up.
And, even if a dog gets his ear torn, or gets a slight cut, or some hair ripped out (all of which will sometimes end a fight), it’s better than having it done to your hand. Remember, It’s not the end of the world to have an injured dog. I’m not talking about an eviscerated dog, but I’ve just never seen it get to that level.
Keep in mind that dog fights are usually about establishing dominance. If one dog thinks he’s done that, it can be over. So separating two dogs will sometimes make one of them think he’s won, so a quick separation is sometimes the end of it.