Calm Greeting
Step 1: This is best practiced first in a distraction-free environment with people who are familiar to your pup. While on leash ask the person you are practicing with to walk calmly up to you and your dog.
Step 2: When they are about 10 feet away, ask your dog to 'sit', then 'mark' and treat.
Step 3: As the person continues to calmly walk forward, keep the treats coming to reinforce the 'sit'.
Step 4: When the person reaches you and your pup, continue to treat 1 treat every second while they are in front of you. Keep this time short to start so as not to overwhelm your dog.
Step 5: Continue these steps increasing the amount of time a person stays in front of you.
Step 6: Once this is solid, increase the distractions by having people act more excited when they come up and eventually working on this when out for walks.
TIP: If your pup is not able to stay in a 'sit' at first, increase the distance between you and the person and reinforce until you are able to gradually bring them closer.