To break up the awkward silence at the start of a recent Overcoming Bias meetup, I asked everyone present to tell their rationalist origin story - a key event or fact that played a role in their first beginning to aspire to rationality. This worked surprisingly well (and I would recommend it for future meetups).
I think I've already told enough of my own origin story on Overcoming Bias: how I was digging in my parents' yard as a kid and found a tarnished silver amulet inscribed with Bayes's Theorem, and how I wore it to bed that night and dreamed of a woman in white, holding an ancient leather-bound book called Judgment Under Uncertainty: Heuristics and Biases (eds. D. Kahneman, P. Slovic, and A. Tversky, 1982)... but there's no need to go into that again.
So, seriously... how did you originally go down that road?
Added: For some odd reason, many of the commenters here seem to have had a single experience in common - namely, at some point, encountering Overcoming Bias... But I'm especially interested in what it takes to get the transition started - crossing the first divide. This would be very valuable knowledge if it can be generalized. If that did happen at OB, please try to specify what was the crucial "Aha!" insight (down to the specific post if possible).
I bet my experience is pretty typical: it's just been one really long of string of oops, as far back as I can remember. I realized I was wrong, I updated. I started with nothing... no beliefs, just professions that I think I realized were transient. Slowly but surely I converged on agnostic Buddhist Epicureanism with a little Sagan, then atheist scientific liberal majoritarianism at RationalWiki with a little Dawkins, then neorationality here with Yvain and Eliezer, then hyperrationality at SIAI with a whole bunch of really strong thinkers, and now I just keep on working at it. Lately I've been reading a lot of source materials (Tooby/Cosmides, Dawkins, Jaynes, Buddha) and asking a lot of "Why do I believe what I believe?"s which have both been rather useful at sharpening my thinking. I'm not sure where to go from here; keep learning math, I guess? Read more source materials? I think I'm getting diminishing marginal returns and might soon start having to really paint my own art. That said, at this point it seems the true field of battle will be on the front of instrumental rationality.