I have one tried-and-true method that works quite well for family members (but it would be difficult to ask a guest to do this!): grab the dog's paws as he/she is starting to jump on you. Take one front paw in each hand, and gently place the dog's paws back on the ground while saying "off" (or another command you're comfortable with). The word doesn't matter, it's your tone of voice that matters. Say it like you mean it, but stay calm and gentle.
At the same time, ignore the dog and "claim your space". This is a trick I learned from watching Cesar Millan. I know a lot of people don't like him, but some of his stuff is just normal and not controversial, so let's just stay there and not get into any of that b.s. Cesar demonstrates "claiming your space" on many episodes of his former TV show, "Dog Whisperer with Cesar Millan".
We "claim our space" all the time when we interact with humans, we just don't know it because we do it naturally. Do you like your specific seat in the classroom, at the bar, restaurant, or in the living room? You just gravitate towards that seat with inborn intention. You don't think about it, you don't say anything about it, you just do it. The same is true with dogs, take some time to observe dogs claiming their space with each other (or with humans LOL!). If you have more than one dog, or dogs and cats, watch how they interact and claim their space with each other when they go into and out of rooms, through doorways, and (if allowed) up on furniture. Notice how one animal is usually the "leader" and he or she goes through the doorway first, goes into or out of a room first, goes down or up a stairway first, etc. The others defer to the leader. Well, you should be the leader!
Let's focus again on jumping on people at the front door, and forget about "at the dog park" or other places for the time being. The first thing the humans in the family should do is claim the door and its surrounding space as their very own. Barge into the house like you own the place, because... well, you DO! Don't do it with anger, but do it with intention. What this means is you have to mean what you say with your body language and your energy. If you are all wimpy with your hands held up in a no-no-no fashion, and you're saying "off! Off! OFF!" and you try to barge into the house, the dogs are only going to pick up on your wimpy energy and you trying to protect your body with your no-no-no hands (and your voice). Don't say anything, just walk confidently into the house and put your purse down, take your coat and shoes off, whatever it is that you do when you enter your home. At first, you may have to grab the dog's paws as I mentioned before, and place them firmly on the ground (but with good energy inside yourself, just be calm). After you've done this for a few days, you should start to see results. Remember, patience and calmness is key in training a dog, or breaking a bad habit such as jumping. It is not going to change overnight. Be patient, dogs are smart, they will get it.
Once you've successfully "claimed" the door, most dogs will learn stay back in the room when guests come over. But not all dogs!
Just remember, it's your door, it's your kitchen or living room or mud room, it's your house. Just walk right in and ignore the dog.
This is just another video I found online demonstrating how to claim your space at the front door with three dogs. Notice how the gentleman walks in like he owns the place, and the dogs respectfully give him enough room to enter the building. Then, he demonstrates how to stop them from jumping by just putting his hand out. This is the type of technique you want to master, if possible.