...but here goes anyway... The textbook way: by being exposed to views, information, facts, and just plain insightful analysis of culture, history and politics from people I'd never rubbed elbows with until I came across them online.
Sheltered religious childhood, sheltered conservative ecosystem of family, friends, and school. My first online forum in 2002 was a conservative one where non-conservatives were banned on sight. Psychological reinforcement bouncing off all surfaces of the silo. It carried me through the Kerry swiftboating, Florida recount, the Iraq war, the Obama birth certificate...
In 2009 I left that forum and found another one that was still extremely right wing and religious and with a political section similar to this forum in that (unlike this forum which is well moderated) it grudgingly allowed (but then frequently banned) non-conservative ideologies, and that was literally the first time (I didn't go to college until many years after high school) I'd been exposed to a more liberal, open, questioning, scientific and less dogmatic, less rigid way of looking at the world around me in every aspect of human experience. I made some friends who were very patient with me, and we sparred often in the same way we do here, but when I began to realize that they made sense, their information was supported, their experience was valid, and that I cared about them regardless of whether we had much of anything in common at all or not, I turned around and started looking back at myself, at what I believed - from their vantage point. I'm not at that forum anymore either, but my life was changed in those years. Ironically, I found my way out of conservatism on a conservative site.
I left the GOP in 2012, and am an independent, or NPP as they say in California, but since 2012, I've voted a straight Democratic ticket.
Now I look back, and wonder how did I let myself be so brainwashed? How did I not question? And all I can say is I was raised to obey authority, to be docile - and years later, in my Psychology of Prejudice and Stereotypes class in university, I saw the telltale traits of right-wing authoritarian personalities and I recognized them all too well. I could write a good bit more but I'll leave it at that.