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 believed very strongly that my mind was not functioning correctly and I wanted to find techniques to be able to sort through what was real and not real. This led me to begin a very rigorous program of self-examination where I picked at and questioned everything that I am and might become. I continue to do this now but I have learned that I at least seem surprisingly sane compared to my previous view of my self. I have also always had a very strong sense of curiosity tied up with a very impulsive nature. Over time I just experimented with all sorts of things with not much fear of the consequences.
What really turned me on to rationalism specifically was Eliezer's posting on Overcoming Bias. He inspired me to try to go into the field of math and science in large part because I couldn't understand barely anything he said and what I did understand supported several pre-conceived notions I held that made me feel superior to other people.
Trying to fix that now. Yep.