Matt has a great post up on his history with beer. It's chock full of beer lore and some interesting musings on the fact that beer seems to be such an acquired taste. I know it was for me.
I had one or two adolescent encounters (and I say "adolescent" from my current viewpoint; I would have bristled at the term when I was 19...) that resulted in the expected bout of yelling at my shoes. As a result, I couldn't stand the stuff for years. I think the necessary sea change came when I was living with my ex. We were both inveterate computer gamers, and he was a serious coffee drinker. Add the two together, and between the two of us several pots of coffee could vanish in the course of a Friday or Saturday, my share of which was drunk black.
"Bitter" is not a taste sensation the young normally seek out, but several zillion cups of black coffee will make you a connoisseur of bitter. Good coffee bitter. Bad coffee bitter. This-coffee-is-burned bitter... A year later, after a sweltering summer day working at the gun shop, which was in a tin-roofed building with two glass walls and no A/C, my boss offered me a beer after we'd shut down. I seem to recall it was a Miller Genuine Draft in a bottle. I remember it was very cold, and very wet, and boy did it hit the spot. And hey, it didn't even taste bad!
Still, it remained a hot weather beverage for me. Nothing I'd seek out for the taste, specifically, mind you. It was another couple years until a friend introduced me to Whitbread Ale on draft at a local pub. This was actually tasty; something you'd drink just for the pleasure of drinking it, not just to cool off on a hot day. From there, it was a just a short hop to Bass and Sweetwater 420 IPA, Mendocino White Hawk and Stone Ruination, IPA's and Barleywines.
Anyhow, Matt, that's how it happened for me.