When I was a kid, most of my D&D material came from one of the local discount stores. There was Van Leunen's, and there was K-Mart (yes, the same K-Mart that makes Walmart look like Macy's). Both stocked D&D in a special section next to the toys. When I began to accumulate MERP/RM stuff back in my senior year of high school, I got it from the local Waldenbooks.
Now that I think about it, all three destinations are gone.
I didn't set foot into a game or comic shop until college, when I started going to The Tin Soldier. If I'd have been looking at games at The Tin Soldier first, I might not have stuck with the hobby, because they used to treat kids as either people who destroy minis battles or thieves waiting for an opportunity. The discount stores and the book store left me alone to peruse at leisure. Maybe they were watching me, but my kid radar didn't go off.