Guys scout out the fraternities they are interested in around this time of year. Some start rush events after Christmas break but now is when it gets serious.
From rush events you decide which frat (or frats, although only one is recommended, at least at my college) you would like to pledge to. Pledging consists of all those nasty hazing things. Pledging starts at my college fall semester of sophomore year.
From the pledge class the existing fraternity brothers extend bids to those they would like to accept into their fraternity. This happens a bit before winter break of sophomore year.

Some frats require a certain GPA. Actually, most do, some just have atypically high ones.
You must do so many community service hours.
You will have to pay dues, depending on the frat/school they can be terribly high. You're also expected to give money every year or so after you have graduated and established yourself.
Even if the frat you're looking at says they don't haze, they're really lying. It may not be too bad, with the exception of Hell Week which is a much loved sport among brothers. Most Hell Week stories I've encountered involve living out of a box. Hazing is basically necessary when joining a frat, as the whole point is to make the pledge class hate the pledge master, therefore forcing them to bond.
Not sure about your college, but where I go it's basically required you play a sport, and certain frats are known for certain sports. Like Fiji is typically rugby and hockey, and TKE is lax.

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your whole life is leading up to this