From Cesar Milan’s Dog Psych Series
When you yell, or worse, at your pooch to stop barking when the doorbell rings, first, understand what is happening from your dog’s point of view – what they are learning is, “Doorbell means my humans will attack me,” and that is not the idea you want them to have.
Using the sound of the doorbell is a good tool to use, but it is only one tool. Make sure that you associate that sound with something calm and pleasant for your dog. If your dog is already trained to sit calmly before receiving treats from you, you’re halfway there.
What you need to do is get them to sit calmly for a treat first, then ring the doorbell. If they do not react to it, they get the treat. If they do react, redirect them with the smell of the treat (but don’t give it to them yet), get them to sit calmly and wait, then repeat the process.
In this way, you will teach them that “doorbell = treat,” but only if they sit calmly. You’ll also want everyone in the house to have treats on them at first, so that when the doorbell rings at random they can reward the dogs that comply right away.
Eventually, you’ll be able to do away with the treats. And, if you have more than one dog; focus on the most dominant one in the training; this will help you in training all at once.
You can read this advice written by Cesar Milan and more at www.cesarsway.com