A professional (find one through The Pet Professional Guild) can help you train your dog to trust his environment and handler when he is on leash. Dogs can feel trapped by that lifeline. It’s vital that we teach them how we want them to behave when they see other dogs. These behaviors first must be taught in a safe, controlled setting such as a dog-training center.
If your pup barks: Some dogs have the habit of barking at other dogs while on a walk. Oftentimes, this behavior comes as a result of lack of exercise. Make sure your dog gets the proper amount of mental and physical stimulation for his age and breed. If this is still a problem, use the same process as you would if your dog is lunging, as described above — create distance and offer treats before he starts to bark, so every time he sees a dog he gets used to turning his attention to you.
Throw a meat treat in the direction of the oncoming dog, turn on your heels, and walk away. I cannot even count the number of dog owners who are shocked that as their dog is being harassed by the off-leash dog, the owner of stands there, saying nothing, and doesn’t help to put an end to the situation. If another person is walking with you, ask them to attempt to catch the oncoming dog as you leave the scene (you have to decide in an instant if that would be a safe maneuver or not because breaking up a dog fight is an excellent way to get bitten).