On Tuesday night, Iowa Republicans will gather at 1,774 locations around the state to kick off the 2012 presidential election, through an "idiosyncratic" caucus process with origins at least as old as the United States. Unlike more straightforward primary elections, the voters who brave the cold Iowa winter to spend a weekday evening politicking won't award any delegates to the winning candidates. Adding to the unusual nature of the caucuses, each of Iowa's 1,774 precincts gets to set its own rules. Still, despite the quirks and arcane rules, "Iowans stand by their caucuses," says Elizabeth Hartfield at ABC News. Here, a guide to the proud, strange Hawkeye State electoral tradition:

How do the caucuses work?
Caucus participants gather at their local precinct meeting place — usually a school, library, church, or other public space, but sometimes a private home — by 7 p.m. Then, after reciting the Pledge of Allegiance and electing a caucus chairman and secretary, the caucusgoers listen to a brief endorsement speech by a surrogate from any campaign that sends a representative. Then Iowans vote: Republicans note their preference by secret ballot, usually a blank slip of paper. The votes are counted in public, read aloud, then phoned in to the state GOP, which tallies the statewide results and releases them.

Who can participate?
Any registered Republican who lives in the precinct and will be 18 by Election Day. But since state law allows voters to switch registration at the caucuses themselves, the event is effectively open to all interested voters. Turnout isn't usually very large, though. In 2008, about 120,000 people cast ballots in the Iowa GOP caucuses — roughly 21 percent of active registered Republicans — while 227,000 Democrats caucused to decide that year's heated battle between Barack Obama and Hillary Clinton. Political analysts expect a slight uptick on the GOP side this year.

Are the Democrats also caucusing on Tuesday?
Yes. But since President Obama is essentially running unopposed, "the Democrats who go to their competition-free caucuses are the ultimate loyalists," says Linda Feldmann in The Christian Science Monitor. Unlike Republicans, Iowa Democrats pick their candidates in public, typically with supporters of each candidate standing together in different parts of a room for a headcount. Since there will be no drama over who wins on the Democratic side, the caucuses will focus on party business and organizing for the general election.

What do the caucuses accomplish?
Despite all the media attention, caucusgoers' presidential preferences are non-binding. The real business takes place after the presidential vote, when the caucusgoers who stick around pick delegates and platform proposals for their county GOP convention. The 99 county conventions will later select delegates to the four district conclaves, each of which chooses three national delegates and two more for the June 12 state GOP convention, where the remaining 13 uncommitted national delegates are finally selected. Three high-ranking Iowa GOP leaders are automatic delegates. It's these two dozen or so delegates who will vote for a nominee at the national GOP's summer convention in Florida.

So why do Iowans still caucus?
It's partly tradition: Iowans have always caucused, except in 1916, when they tried switching to a presidential primary. (No major candidates participated and voter turnout was low, so Iowans switched back.) Caucuses are also less expensive to mount than primary elections. And in staging what amounts to a "glorified poll," Iowans actually "get the best of both worlds," says David Sessions at The Daily Beast. The press treats Iowa's first-in-the-nation presidential opinions as significant, but since those first picks may not survive long, Iowa's national convention delegates get to pick from whichever candidates shine in, or at least survive, the primary process.

Why does Iowa get to go first?
Thanks largely to an accident of history: In 1972, Iowa Democrats pushed the caucuses back to Jan. 24 because a reformist state party chairman wanted Iowans to have a copy of the rules, and the mimeographing and mailing of the paperwork required 120 days before the state's May 20 convention. The Republican Party joined in the leapfrogging of New Hampshire's primary in 1976. "Forty years ago, Iowa officials never anticipated that the precinct caucuses would attract such a high profile," says Greg Giroux at Bloomberg. "They now guard their first-in-the-nation status for the national attention the caucuses attract." The national parties codified Iowa's special status in 1981.

Sources: ABC News, AP, Bloomberg (2), Christian Science Monitor, Daily Beast, New York Times (2), Washington Post