The first time you jump out of an airplane at 5,000 feet, you're petrified. By the 500th time, it becomes blase' and old hat. The first stranger your dog meets is going to be scary. Once the dog is a bit older, the method is the same but the approach is slightly different. Obviously, the more nice people your dog meets, the more he will begin to see strangers as nice folks.
Quantity is very important here.
Quality of encounter is also very important. All meetings with strangers should be as upbeat and positive as possible. Oftentimes, this means that the strangers engage in play or give treats to the dog. If your dog is a food mongrel, then a treat from a stranger will make all the difference in the world. If your dog is a Frisbee nut, then a few tosses from each person will help break the ice.