The thing about Petco is that you can bring your pet into the store as long as they have a leash. So it allows you to take a puppy into an environment that is rich in sound, smell and people while at the same time it is a controlled atmosphere.
Now, I have ferrets and have done some shopping for their food and litter in the store, but to be honest, most of it is done online. (Due to the prices being a lot less; as long as I don’t forget to actually order it.)
Anyway, I digress, so took the puppy into the store for the first time and he did amazingly well. It helps that we have been working with him on the leash since we first got him. Although he hasn’t learned to heel yet and still pulls from a lot more than he should but that is due to our not working with him as much as we need to.
He met a couple of people who work in the store as well as another small dog that was there. He wanted to play but the dachshund didn’t want anything to do with him. However, he didn’t try to pull anything off of the shelves, or roam. He sat for a treat and people were courteous enough to ask before petting him.

I met one of the dog trainers and am considering puppy kindergarten for him. I haven’t fully decided as I have never actually taken any of my dogs to training classes and have done it myself; with very positive results. Yet, I am interested to see how they do it and this would present a very good opportunity. I already have been working on socializing him, and am taking it slow as he still hasn’t had all of his shots. (State law is 16 weeks here.) So, we are waiting that out, while allowing him to experience different environments; sounds, people, places.