Does your dog get overexcited or lunge forward in the presence of other dogs while on leash? Sometimes it is fear aggression and sometimes it is an over enthusiastic response by a very social dog who wants to play. Either way, the resulting behavior is unpleasant. Here are a couple quick tips:
-1) Provide a highly valued treat when another dog appears but is still far enough away that you can get your dog's attention. Eventually your dog associates the appearance of another dog with something pleasant. Do not try to give a treat when the dog is already in the ZONE- barking and pulling on the lead. You may not get his attention at this point and if he takes the treat, you inadvertently reward the bad behavior.
2) Enlist a neighbor or friend with a calm nonreactive dog to help. Start with enough distance that your dog notices the other dog but is not reacting yet, then work to get your dog to sit and look at you for a treat. If necessary, put more distance between you until you have success, then gradually try shorter distances. Your goal is a calm, nonreactive dog in the presence of other dogs.
Be patient and consistent with your routine as every dog is different.