Is Your Dog a 'Barker'?

First of all, you must ask yourself - do you really want him to completely stop this habit? In today's climate of increased anti social behaviour, i.e., thefts, breaking and entering and unwanted callers you may well need added protection.
This can be a very useful habit for him to have when the house is empty because he will be on guard and in charge. Some companies now manufacture 'dog alarms' - the recorded sound of a dog barking whenever someone knocks at the front door.
Perhaps training him not to do so when you are at home and in charge would be a better idea. After all, you don't keep a dog and bark yourself!
When someone knocks at the door and he starts barking, check whether they are 'friend' or 'foe'. If they are 'friend' put him into the sit position, hold the palm of your hand out flat in front of him and sternly command 'No'. If they are 'foe' or just an unwanted caller do not deter him. After a few times of this repetition with your 'No' command, he should learn what is expected of him. If in doubt - let him bark better safe than sorry.
You can 'test' him when the next time you go out. Close the door as usual, and if you have a car, drive off. Stop a short distance away and then ask a neighbour to go to your house and knock or ring the door bell. You will then see what the dog's reaction is.
You cannot perform this check yourself because the dog will know the sound of your footsteps and also your 'smell'. You will need to ask someone who is not really known to the dog for the experiment to be an accurate test. ( by Jo Withey )