When a dog jumps on a human of its own free will, it is not "greeting" the human, it is asserting its dominance over the human; it is the dog communicating that it is alpha and/or wishes to own/control the human. A subordinate would never dream of running over and jumping on the alpha dog of the pack. Space is respect and lower members of the pack respect the higher members. If your dog jumps on humans, it does not respect them. Note: when a young puppy jumps on humans it is sometimes its attempt to reach one's face. Puppies need to be taught not to jump up on humans as this behavior will manifest into other meanings as the puppy grows up into an adult dog.
Before you answer the door and welcome guests, clip a leash on your canine, preferably to a front-clip harness or head halter, so that he can be controlled in a manner such that he cannot greet if he jumps. When your dog is calm, with all four paws on the floor — which may take up to a few minutes for more excitable dogs — allow him to approach guests and say hello. If he jumps, gently turn and lead him away; wait for calm behavior before approaching again. For particularly excitable dogs, another option is to remove the dog to a contained area before guests come in. An exercise pen or baby gate is adequate containment for many dogs. If you have an athletic or large dog that can easily scale a gate, use a crate or move him to a room with a closed door. Once your dog calms down, clip on his leash and allow him to come out and greet your guests.
Redirect with a sit command. The simple 'sit' command can be useful in many different situations. Most importantly, it is a great distraction technique for redirecting your dog's attention from an undesirable behavior, such as jumping up. When your dog jumps up on you, turn your back to them while keeping them in your peripheral vision. Ask her to sit and immediately praise her when she does so.
Teach your puppy a conflicting behavior such as “fetch your ball.” She can’t jump up if she’s running to bring you her ball or favorite toy. Just the name of a special game or toy—“go get your bear!”—can change the dog’s focus and redirect the behavior long enough for you to evade the jumping. With enough repetition, your puppy will begin to associate your home-coming with “go fetch” instead of jumping up.
Paying attention to a dog only when all four paws are on the floor can work well, if jumping isn’t well entrenched and if everybody who deals with the dog follows the rules. Unfortunately, much of humanity will get busy undermining you. “I don’t mind your puppy jumping up,” they say, while you tear your hair out. Or they get all disciplinarian, maybe kneeing the dog in the chest. That is not only mean but counterproductive, because dogs often respond by trying to appease. Since humans are usually taller than dogs, reaching our muzzles to lick them involves jumping up.