Jumping is a natural behavior in dogs.  However, you can give your dog a course in polite greetings when meeting people at the door or in public. 

    Te best way to modify this behavior is to ignore him/her when (s)he jumps up, and reward him/her with treats and attention when (s)he sits.  If (s)he jumps, turn your back and step away so (s)he doesn't even make contact.   This must be done consistently in order for your dog to realize that the consequence of jumping up (turning you back) does not gain the expected results for the dog.  Ask everyone (s)he meets to do the same.  If some people reward him/her for jumping, the behavior will continue. 

    Use a leash to restrain him/her so she can't follow visitors and jump up.  If (s)he jumps on you, step on the leash so its long enough that (s)he can stand comfortably, but short enough to keep him/her from jumping.

    You can also teach your dog that someone at the door means "get a toy."  Ring the doorbell and excitedly encourage him/her to "get the ball" until the bell itself becomes the cue to run and her his/her ball.  Or, keep dog toys at the door for visitors to pick up and toss when they enter.  Your dog's energy and attention will focus on the toys rather than on jumping up.

    If your dog hasn't fully learned polite greetings, use his/her leash to restrain him/her as people enter the house.  To reinforce your training efforts, hand visitors a treat and ask them to approach your dog, wait for him/her to sit, then feed her the treat.  Keep him/her leashed or tethered throughout the visit to prevent him/her from jumping on visitors.

    When you've had enough tethering or leashing, it's OK to excuse your dog from the party.  Put him/her in  an off-limits room with a luscious food-stuffed toy or other chew toy to keep him/her from feeling deprived.