How Can I Get My Dog to Stop Barking at Everyone Who Comes in the Door?

Every time ANYONE…(even my family) enters through a door my dog barks his head off….if its a stranger that he doesn’t know..he keeps barking..he is almost 4 years old..is a pomeranian and is quite small..we think he barks because he is scared…because when he barks he runs right away from the person.. we think he is scared because he might of been abused by his previous owner… um he has done this barking since we got him when he was almost 1…what can we do to make him stop without using a shock collar?

thanks.. mahogany.
he isn’t left alone at all..there is always someone home..if not he is left alone for maybe an hour a day..and is always playful
um…all he does when you try to stop him from barking is run around the house……we can’t get him close to them really….please help!
one other problem is that my uncle sleeps down stairs during the day..so we can’t have him barking excesivly