How do I stop a 7 month old GSD from barking?  Anytime anyone rings the door bell he barks which is OK, but he will not stop barking all the time the person is at the door or even when they come in to the house.  Any help appreciated.

Will he go to his bed when asked?  If you can repeat this excercise each time the doorbell rings (get some friends over to help if possible) he'll learn what you *do* want him to do instead of making up his own rules ;)

Teach the dog to bark on command and then either never give the command or, in your particular case, teach the dog to cease on command too.