I know it was in early 2001 sometime, I just can't remember the specifics. I assume on the internet somewhere. I know I heard that The WB was coming out with a show about a teenaged Clark Kent. I also remember that first thing I actually saw of it was a preview image of the scene with Clark and Lana at the cemetery. Now, given my impressions of what WB programming was like, I assumed that it would mostly be typical teen angst stuff, with a little bit of emerging super-powers thrown in. I still planned on checking it out anyway, because it was Superman for Pete's sake. Thankfully, the angst/superhero ratio wasn't as bad as I thought it would be (though there still was plenty of the former).
I've been watching since day one. Over 9 straight years.