Dogs jump up to greet people for a couple different reasons. They will jump because they are excited, want attention, or because they want to get closer to your face.
Most puppies have been positively reinforced for jumping up from a young age because it is hard not to pet and talk to a cute little puppy when they run up with their tail wagging, thrilled to see you, and put their little paws on your ankles. The only problem is getting bigger and putting their paws on higher body parts.
Teach your puppy how to greet people politely:
Teach the puppy/dog to sit using its food as a lure and reward. Make sure that you practice the sit command in any area you expect the dog to sit to greet people. Have the dog confined or at least on leash while you invite the visitor in and get settled so that the room has calmed down.
Lead the dog, who is on a collar with a leash attached, up to the visitor. Make sure you hold the collar or stand on the leash to prevent the dog from jumping up. Give the dog the ‘sit’ command. Have the visitor wait until the dog sits before giving them attention in a calm manner.
If the dog does not sit right away, just make sure that nothing happens until the dog sits. The first time you do this, be prepared to wait. As soon as the dog sits the visitor should give the dog attention and you may also give the dog a treat as a reward. Next, walk the dog away from the visitor, return and repeat the procedure. The dog is going to be very excited the first time they greet the visitor. After several times doing this, your guest will be old news and you can give your dog a toy or chew to entertain them while you entertain your guest.
If you do this with every family member and every visitor, you will soon have a dog that will sit in front of visitors to get petted and get their attention. It can be tough to be consistent, but it sure does pay off!