You're walking your dog on-lead (leash) and you come upon another dog with its owner. Your dog reacts by growling, lunging, barking, etc. So you pull back hard on your lead yelling "No!". First, that's a normal response, but the incorrect one. When we pull back we place tension on the dog's collar and send a negative message to our dog. We tell him that the dog is bad! Therefore, we reinforce our dog's reactive behavior. Miss Pretty will do it again and again. Yelling no sounds like barking in her ear and will reinforce her further as if we are barking along. What to do instead: it can depend if she's scared, protective of her owner or acting like she owns the land (dominant). Best to seek help from an experienced trainer or behaviorist to apply behavior modification techniques. Until that's possible or at the very least, try to move closer to your dog allowing less tension on Ruff-Ruff's collar putting yourself in a better position to control the encounter. Move your dog away and in another direction to lessen the impact of the reactivity on the reinforcing factors. Plus you will allow your dog to calm down more quickly because he's not stuck in the situation. That won't rehabilitate the dog like a professional can but at least you'll have a plan of action until then.