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.
Our inconsistency perpetuates the problem. Some of the time we tolerate the jumping and ignore it. Other times we reward the behavior by exchanging enthusiastic greetings. But when we're dressed up and the puppy's paws are muddy, it's a different story. Reprimanding the puppy for jumping up usually does not work. Either the puppy misunderstands the reprimand as praise or he gets even more excited and the jumping gets worse. If the reprimand is severe enough, the puppy may stop jumping at that moment but it doesn't solve the problem altogether; and it certainly is not a very nice thing to do. It's very similar to a person approaching you with a big smile, arm extended to exchange a hand-shake and you bopping the person in the nose. Even if your puppy learns that jumping up on you is not a good idea, he will usually get away with jumping up on everyone else.
If a dog is stressed or afraid, their demeanor and typical behaviors will change. If you see this in your dog (or really any dog you know) you should step back and check on your dog. Are they hurt? Did a new dog come around they don’t know? Has the weather changed? Is it hot outside? When was the last time they had a chance to go outside to pee or poop?
1. To assert dominance. Whether it's jumping on people or jumping on furniture, both instances illustrate a dog that wants to raise his station in life. By jumping on you or jumping on the couch, he's saying that he's the pack leader--something that you DON'T want to happen, as a dominant dog is much more difficult to train (and can become quite aggressive). In either case, you'll definitely want to institute the proper alpha dog training techniques, if you haven't already.
Unless given a command to jump, a dog should never be allowed to jump on humans. A dog that jumps on humans of its own free will is a dog that does not respect the person it is jumping on. Even those cute little toy dogs should not be allowed to jump on people. While you may think it is cute, it is not cute to everyone else. Not only is it annoying to most people to have someone else's dog jump on them, it can also be dangerous. A jumping dog can knock people over, muddy their clothes, put runners in nylons and scratch the skin.