1. I think I became a Republican just by filling out a voter registration card
Although that was a long time ago, and I cannot remember voting in a primary election. There was a primary that year, between Reagan and Bush, among others, but I cannot remember voting in it. My parents were Republicans too. I remember mom was a fan of Bush Sr. Perhaps the primary was over before it got to SD. Then in 1984 I registered in Minnesota where I was going to college, but cannot remember specifying a party, although I did vote for Mondale that year (not on purpose, I actually flippd an Eisenhower dollar in the voting booth and it came up heads, had it been tails, I'd have voted for Reagan again. I was slow to wean myself away from the Republicans.) By 1988 though, having moved to Utah, back to SD, and finally to Wisconsin, I was definitely a registered Democrat, because I voted for Jesse Jackson in the presidential primary that year.
And that is how I became a Democrat (at least the condensed version, I did not mention being blown away by Jesse's convention speech and watching Reagan flounder around in the debates, and reading lots of Vonnegut, Studs Terkel, and also entering the workforce) - a party I previously had referred to as the dumbocrats.