A very common behavior issue that we see in dogs is reactivity (barking, lunging, snapping, alerting) towards other dogs or strangers when out on leash. Dogs react to various triggers for one of 2 reasons: (1)they are nervous or fearful of the oncoming person/dog and would like it to go away or (2)they are frustrated that the leash is stopping them from greeting the person/dog. It is difficult to tell which of these reasons your dog has for reacting, but just because they are reactive does not necessarily mean that that the dog is unfriendly or aggressive. If you do not know what your dog's desired outcome is from this interaction, reach out to a local trainer or behavior specialist to help assess the situation.
Regardless of what is motivating your reactive dog, the best way to help them is to give them an alternate way to communicate their desired outcome. Doing this requires help from a trainer to make a plan best suited to your dog (email firstname.lastname@example.org for recommendations). While waiting for a trainer's help there are a few things you can do to make sure the problem is not worsening:
Avoid potential triggers when out on leash with your dog. If you see your dog begin to react, move farther away from the trigger as much as possible.
If your dog is in the middle of a reaction, stay calm and stay in place (as long as you have your dog secured). Simply wait for the dogs reaction to stop or improve and then guide them away from the situation. Rushing away when your dog is in the middle of a reaction can increase reactivity in the future.
If you see a potential trigger from a distance and your dog does not react, reward them with treats and praise and move away from the potential trigger.
Walk your dog using a front clip harness to be able to have more control of their body while on walks.
It is important not to punish your dog for reacting as this can build negative feelings towards the trigger (they could now associate the trigger with getting punished).
Doing these things will help your dog start the process of reactivity training, but please contact us or a trainer for more help.