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.
Start by teaching your puppy the word NO. Use that word only when she is doing something you do not like. You have to use the word NO in a loud, stern voice that is different from all other ways you communicate with her, so that she knows there is something wrong. You also have to catch her in the act that you don't like, so that it will associate the word NO with the action that she is doing. Be consistent, and follow your verbal command with a light smack or moving her to a time out spot.
Determining if this is your dog is a little more complicated, but it is often seen when your dog isn’t very excited (or that there isn’t much of a reason to be excited). This is more than likely to happen when you are in their way or have something that they want. They will usually jump on you and try to push you back more than just jumping up to give you kisses. Often times they will jump on you and try to hold on when you push them away or try to move into them. Sometimes moving into them may elicit a growl because they want to back you off.
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.
In order to perfect the proper greeting routine, your dog needs much more practice than that. You can speed up the training process by leaving through the back door and returning through the front door over and over again. When your friends come over, have them do the same. Each time, ask your dog to sit-stay before opening the door. At first his excitement will make it difficult for him to concentrate but after you've repeated this process 10 times, he will calm down and be able to concentrate. Before asking your dog to sit-stay in this distracting and exciting situation, be sure he has a reliable sit-stay in normal, non-stressful situations. And of course you can always just hold the dog in a sit if need be.
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.