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).
How rational was your transition to rationality? A sudden transition seems more suspicious, as that looks a lot like the sudden transitions humans tend to make between social groups. After all, there is usually little social benefit to sitting between social groups; social rewards come more to those firmly within one group or another. A gradual transition, on the other hand, seems more plausibly to match the more steady rate at which relevant info arrives on such topics. How much more relevant info could you really have obtained via one story or essay? Whatever your conscious thoughts, if you had a sudden transition I'm guessing that was your subconsious mind thinking something like "Yes, this looks like a good social group to join."