A conflicting behavior when you come home—like “sit”—helps enormously. You’ll need to practice your puppy’s “sit” during calm moments first, and then ask for this polite behavior before you leave and when you arrive home. Guests will appreciate a polite “sit” when they arrive, too, as they won’t appreciate your puppy leaping around and mugging them for attention.
Nobody likes to have a handful of groceries knocked out of their hand or get muddy paw prints on their new pants as they walk through their own front door, let alone someone else's front door. Jumping up can be a cute greeting when you have a small puppy or dog at home, but as time goes on, it can become quite annoying to you and your guests. Teaching your dog to calmly greet you and your guests, without jumping, will create a much more enjoyable environment to enter into after a long day at work or when receiving guests at home.
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.
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.