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 grew up in a Reconstructionist Jewish household with an Orthodox dad and an Israeli mom. I'm sure they used to think that I'd become this great Jew - I was sent to a Jewish private school, and I realise now that I was (and still am) a perfectionist, which meant I felt the need to do all the prayers and ceremonies properly. The first push towards rationality came sometime in second grade, when I asked my parents if I was adopted (long story) because I'd never heard a solid answer in either direction from them before. When they said I was and that they hadn't been intending on telling me, something in me must have started ticking towards science and rationality, because that was when I discovered that adults lie to their children.
I started noticing the lack of evidence for events from the Torah, and even from the rabbinical tales. Science, on the other hand, had rocks that dated back millions of years, or bones from animals never mentioned in the Torah. Armed with that knowledge, I realised the idea that one being (god) being lord and master over the whole universe didn't make sense. So I dedicated myself to science and became an atheist, or at the very most agnostic. I started holding truth-with-evidence as best thing to do, having noticed the general hypocrisy I was being surrounded by in school and at home.
In middle school and high school I managed to find my way into Wicca and Paganism, more interested in the idea that magic could be real (fantasy books have always been my favourites) than in the mythology and deities involved. Somehow over the years that morphed into belief-in-belief (which I only realised yesterday after encountering the self-deception posts).
College saw me reading anything and everything I could get my hands on, and changing my major three times. I tried computer science, astrophysics, theatre, linguistics, and criminology. I took classes in psychology, statistics, programming, physics, backstage rigging, and so much more besides. I kept up with science magazines like Discover and Scientific American, reading them from cover to cover to absorb as much scientific knowledge as possible. Religion of any sort fell by the wayside and was mostly forgotten aside from the bonfire holidays and Halloween.
After college I found HPMOR while on a fanfiction marathon and that's what really got me started down the road. Reading about Harry and his thoughts made me want to think and be more like that. Breadcrumbs led me here, and I'd been intending to start the Sequences for the past year or more. A few weeks ago I finally sat down and started the Sequences. And now I'm here and trying to think better.