Dogs play by jumping on one another, it is something of a dominance game. The winner is the one who gets to put his paws on the other. To teach him not to jump you have to teach him that it is not pleasant for him to jump on people and that it is more pleasant to have all 4 feet on the ground.
To make it unpleasant for him to jump on people, one of the best tricks is to raise your knee as he jumps, so it hits him in the chest. When he has all his feet on the ground you reward him by patting him telling him what a good dog he is, maybe even giving him a treat. This will teach him to greet people with his feet on the ground.
Remember that you have to be consistent. Don't allow him to jump on anybody, not even people who say they don't mind.