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).
Apologies for coming to this party a bit late. Particularly as I find my own answer really, really frustrating. While I wouldn't say it was an origin per se, getting into reading Overcoming Bias daily a few years back was what crystallised it for me. I'd find myself constantly somewhere between "well, yeah, of course" and "ohhhhhhhhhhhhhhh!" Guess the human brain doesn't tend to do Damascene revelations. We need overwhelming evidence, over a long period of time, to even begin chipping away at our craziest beliefs, and even then it's a step-by-step process.
The analogy I sometimes go over is something most people find fairly obvious like egalitarianism. You don't find many people who would attest to being pro-inequality. But all the same, you find very few people who have genuinely thought through what it means to be in favour of equality and really try to fit that into everyday life. The first step to becoming a rationalist is to admit how irrational everyone is without monumental efforts to the contrary.
BTW, I am totally on the road to de-Catholicising my mother. This is on the order of converting Dubya to Islam, so if I can manage that I'm awarding myself an honorary brown belt.
WRT to de-Catholicising your mother: it has been rightly said that Catholicism is the most rational and consistent of all the religions. So, it would be a pity if you dissuaded her from Catholicism and inadvertently landed her in a less rational religion!