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 was born in China, and moved to the US at the age of 10. My parents were both educated in Communist China and therefore atheists. I do not recall any anti-religious education in school, but do have a fairly vivid memory of watching a state-produced television program on the evils of 迷信 (superstition), which somehow left a deep impression.
After moving to the US, I remember watching Star Trek (reruns) as a teenager and admiring the Spock character. But I don't think I ever had a strong interest in learning how to be more rational, and instead just had an intellectual curiosity in topics that happen to be related to rationality, like economics, game theory, cooperation, the nature of probabilities and anthropic reasoning, the future, the Singularity, moral philosophy, etc., which led me to OvercomingBias and then LessWrong. Even now I think I'm driven more by a desire to satisfy my curiosities than to accomplish any larger goals.
I think my experience may be a counterexample to Something to Protect and Try Harder, but I don't really see how to generalize it.