How can you stop prolonged notification barking when guests come?

I've had three rescue/shelter dogs since 1985 and I've taken care of them to the end. One of them would not stop barking when guests came but I guessed that was lack of early socialization. However, I have a relative with the same problem and they got their dog as a young puppy. The barking starts when there is a strange car in the driveway and that is OK, but it doesn't stop until the guests have been in the house for 10 minutes and that is intolerable. I know that training a dog is about repetition but I don't have very many guests and I don't know when someone is going to stop by, so this is something I don't have much control over. I'm going to get a puppy soon and I want the dog to stop barking as soon as I start talking to the guest. How can I train for that?