I think my first exposure to the Golden Age was... paging through old issues of Parents' Magazine that my mother had sitting around in the mid-50s after I learned to read. The magazine ran an annual rating list of comic books (probably inspired by Wertham) that intrigued me no end. By the time I was reading those lists (probably 1957-8 -- 2 to 5 years after the issues were first published), all the "bad" comics were defunct. So they became a kind of Holy Grail of comic books to find.
My second encounter with the Golden Age was when our next door neighbor (an elderly widow) gave me 4 or 5 old comics that had belonged to her (now grown up and moved away) son. These included a Plastic Man and a Blackhawks comic among others. No sooner had I brought these home than my mother confiscated them and put them in the garbage. Jeez! (I searched through the garbage can, but was never able to find them.) This guaranteed that they'd become forever fascinating and sought after.
But my first concrete exposure to a Golden Age comic was my somehow coming upon a coverless copy of an EC Two-Fisted Tales #35 (the Civil War issue) with the heartbreaking "Memphis!" story drawn by Reed Crandall. That story totally inoculized me against the whole genre of romantic/heroic war comics (sorry, Sgt. Rock, et al). Needless to say, all the Mort Weisinger "DC Universe" stories of Superboy, Jimmy Olsen, Lois Lane, etc. that were coming out at the time I read this seemed very lightweight by comparison.