have some friends come over, give each treats or toys which ever the dog perfers.
bring your dog out to see them. Don't have them look at the dog, just at you, and throw the treats on the ground. the dog will see new people = treats = fun.
Then they can come into your house and randomly give out treats and give commands like sit or come and play fetch or whatever if you do this often enough it should work.
It will be come fun, and not important when new people come over.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.