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).
My story isn't very interesting, sadly.
As a very young child*, at Sunday School I was told that prayer was supposed to be a conversation and not a monologue by just me. After a year or two with no one talking back and no other religious experiences to speak of, I began to wonder if there really was someone at the other end.
A year or two later still, I decided that if there was, I would have heard something by now, and became a full-blown atheist. (Although to avoid jeopardizing Christmas and Communion and Easter, and because it'd probably annoy my family, I told no one.)
Everything else - the labels like 'atheist' or 'theist', discovering science fiction, learning logic, reading tons of scriptures and theology and philosophy and occultism - everything else came later.
* I think around age 4 or 5. Surely not after 7.