When Gromette was a puppy, everyone would stop and lavish adoration upon her, particularly women in their late 20s. It got to the point that Gromette would run up to gaggles of women, which I figured could come in handy for my single, dog-sitting friends if I reinforced this behavior with a bit of training. So, I got into the habit of always giving the cutest woman a treat. Making a point of showing Gromette who had the treat, I'd pull her away some distance and then tell her to "Go say hi". She would run up to the woman and get a treat. Now she does it to just about anyone that I point to. Great trick, huh? By the way, I would appreciate it if you would keep this one on the down low as I'm not sure if my wife knows the story behind this one.
Give some treats to an attractive stranger. Make sure that the stranger knows to only give one treat per trick. You'll probably also need some treats to reward recalling your pet to you so that you can repeat and reinforce the trick.
Make sure your dog knows who has treats.
Tell your dog to "Go say hi" and point to the person. Your dog will hopefully assume that this is the go ahead to get a treat from that person. Your attractive stranger might need to provide a little encouragement at first.
The stranger should give your dog a treat, a pat on the head, and should then remove her attention so that you can recall your dog.
Recall your dog to you and repeat the trick.
Eventually, you'll be able to point to people and have your dog run over to say hi. This also comes in handy when your messenger pigeons are on strike.