Dogs are natural warning devices. However, barking should stop when the dog is commanded to do so. Also, when the dog is left alone, barking can be quite annoying to others. Thus, we need to control the behavior when possible.
The best way to stop a behavior from recurring is to associate it with a negative reinforcement. Effective negative reinforcements vary from dog to dog and may depend upon many factors including breed, age, device, timing and more. Some of the methods I use include my voice, or a leash check.
When the dog barks say "Quiet!" in an authoritative voice. This command means to stop barking. If the dog barks again, activate the negative reinforcer such a firm tug on the leash) and repeat the command "Quiet!". If the dog stops barking, praise him.
