Understand the dog's behavior. In a dog's world, it is instinctual to greet another dog by coming nose-to-nose with them. This allows them to sniff each other's faces and become acquainted with the other dog's scent. Of course, your nose is a bit higher to reach so it is only natural that your dog will jump up to get closer to your face when greeting you. This can be quite annoying and unnecessary, but fortunately, the habit can be broken.
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.
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.
When he gives up and stands still (staring at you like you’ve gone crazy), THAT’s when you greet your dog and give him some love and attention. This is the reward he was looking for. Following these rules will ensure he learns that he will only earn that reward by not jumping (don’t overdo the high-pitched voice saying, “GOOD BOYYYYY” or it will just rile your dog up even more to start jumping again).
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.