Again, my first memory of Superman is from the Super Friends cartoon, and he's always been my favorite (aside from having a Robin costume because it seemed more logical as a kid to be a sidekick).
But my first Superman comic? That's really hard to remember. And after some research (thank you Grand Comics Database) it was Action Comics #443.
Reading the synopsis, I remember the story of Superman confusing Brainiac by hypnotizing the world into reversing their knowledge of Clark Kent and Superman. Looking back it's pretty strange (as a lot of that period stories were).
It was a small introduction, and I actually had the Superman #283 from the same month.
Which again was a throwing people off the secret identity trail. I think. The second story with Mr. Mxyzptlk was more memorable with the imp bringing the statue of Abraham Lincoln at the Lincoln Memorial to life.
But it was from these humble beginnings (again thanks to my Dad's friend and his drug store) that my comic collection eventually grew.