Most often this type of behavior is exhibited by puppies, small dogs, or dogs which have never been trained not to jump on people. Dogs will jump up on people for one reason: to get attention from you. This is why when he is a puppy you will want to avoid petting him when he jumps up. Teach your puppy or dog to "sit" for attention or praise of any kind. When he jumps on you, use your lowered tone of voice and lean towards the dog saying "OFF." He will have no choice but to back away from you and when he does, teach him to sit only after he has his bottom firmly planted on the ground. Offer him calm praise for obeying you. Soon all you will have to say to your dog is "sit" and he will comply readily because he knows he will be rewarded.
What if he jumps on you on "the fly" and zips off where you cannot get your hands on him? Attach your leash to his collar and now you are in total control. Tell him "OFF," now "SIT," (help him into this position) now praise him calmly. If you offer too much excited praise you will be giving him the fuel to feed his bad habit, because he will want to jump up again. You cannot expect him to be calm if you are talking to him in your cutest baby talk. Try to avoid situations where you will be setting the dog up in a "no win" situation.