Push him down; knee him in the chest, tell him "off." Ever hear all these directions when you visit a friends house? I've been to many houses where the dog not only joined me on the couch but proceeded to clamor all over me, pull the tie out of my hair and basically sit on the top of my head. All while the owner coached me to "push him off." All of this behavior is no biggy for me; but not everyone wants to be accosted like this. And if I really wasn't comfortable with it all; is it my responsibility to fight off the love attack? No.
The most you should expect from a visitor into your home is for them to ignore the dog. Asking your visitor to ignore the dog is tough enough all on it's own. Now of course if the dog is delivering a powerhouse UFC style greeting; ignoring is going to simply leave your guest unprotected. So it is up to you; the owner to control your dog and protect your guest. You cannot throw your hands in the air and give up; you gotta grab the bull by the horns and control that greeting beast. Often the ignoring routine works wonders; it can build confidence in a fearful dog and take the wind out of a pushy type but for those who loose it when visitors come over, ignoring may not be enough.
So what are you to do if you have an overly exuberant greeter? Training, training, training. Before you can expect even the smallest advance in behavior you must prepare for the scenario. By using baby steps you teach your dog the greeting procedure. My favorite procedure is to teach your dog to assume a "place" position at the bell ringing stage. They are taught to stay in the spot until released by you. The place should be located so that the dog can see the front door but far enough away so that they can achieve success. This does several things to help. First; it gives your dog something to do. You cannot just say to many dogs "stop going crazy." Without going crazy they don't know what else to do. So we give them; "place" and reward them for doing it.
Next; it lets the dog get accustom to a visitor in the house while they are at a distance. They have time to acclimate; time to calm themselves. Release time is up to you; but I suggest you wait for a "chill" state before releasing the hounds. All of this training must be done without anyone in the house; it has to be rock solid before even attempting the ringing stage. Once you add a visitor you must do it in baby steps as well or you are simply setting your dog up for failure. Train for success. If you train hard and make it very positive then when you do add the bell, it becomes the cue to go to their place.
I remember working with a little 4 mos. old black lab. She was just the best "place" dog ever and so enthusiastic. She loved the place exercise so much I swear she was smiling the whole time; I know I was. Watching this little gal charge to her bed at the sound of the door bell, truly amazing. There she sat with a big grin on her face awaiting her reward.
You can teach several visitor etiquette scenarios to your dog. Another could be that your dog sits by the door and stays there until released. You could send them up a set of stairs out of the way to wait on a landing until released. You can train many different scenarios and use them all. When you do release your dog; they should be allowed to offer a somewhat calm greeting to your guest who is hopefully not doing their own form of exuberant greeting and destroying all of your hard work.
Once you get into the training routine the skies the limit.