This behavior can creep up on you, because at first, getting jumped on seems sort of cute. A dog that leaps up on you is very clearly demonstrating his unbridled affection for you, and we like to be on the receiving end of all that love. So we nurture it with pats, laughter and encouragement, and our dogs learn that we like it when they hop all over us. Then, something changes — be it a growth spurt from puppy to adult dog, a job change that requires wearing nice clothing every day, an injury, or a new baby in the house — and suddenly, the jumping up is not only a nuisance, it can also be dangerous. But try to tell that to your dog, who loves interacting with you this way!
To curb a dedicated jumper, simply stop acknowledging the behavior (a warning: it’s not as easy as it sounds). Any attention counts, so refrain from even scolding your dog when he leaps on you. Wait for a moment of calm when your dog has four paws on the floor — it might be literally just a moment at first — and interact with him at that point. If he jumps up again, turn your back until he stops, then resume contact. Leash your dog and step on the midpoint of the leash if he likes to jump on your guests. That way he can mingle with people without delivering a paw to the gut.