I am getting a German Shepherd and want to properly socialize him.?

I take my dog, a labrador, to parks and pet stores often, after all shots are done of course. Kids love parks and love pet stores and i ALWAYS run into them there. I also run into elderly in wheelchairs, little people, other dogs, people of all races and even a possum on a leash once. He is VERY tolerant now, sits well to be petted and knows how to act with children very well. Puppy kindergarten is also a GREAT experience.