My Method: Motivational, positive reinforcement using treats, but also functional rewards. Emphasis is on making the dog feel safe and providing the platform for him/her to learn desired behaviors. You don't have to use a clicker.

I do not use aversive tools like a choke, prong or shock collar, or a nose harness. Why? Because behavioral problems manifest when:

A dog feels threatened (whether he is, is irrelevant--how he feels is what dictates behaviour)

When she is frustrated (the two levels up are anger and rage)

When he is overstimulated 

When she is not feeling well

Obviously, adding more distress by deliberately inflicting pain or discomfort, or threaten a dog with it, is not just unethical but also counterproductive. Even if you quelled the unwanted expressions, the root problem still exits, or worsens. 

Veterinarian and Applied Animal Behaviorist Dr. Karen Overall writes: "The use of shock in the treatment of behavioral conditions is abusive, is doomed to fail, and will make situations less, not more, safe and reliable". She states that dogs that had been shocked to treat aggression are at an increased risk for euthanasia. (Manual of Clinical Behavioral Medicine - 2013 Edition - Page 113).