The nightlife on campus is dominated by parties with Greek affiliation, and for good reason. On a campus this size, the only practical place to have large groups of thirsty people party is in the basement or general vicinity of a fraternity. TKE throws the occasional themed party, and those are always the most fun. Black-light parties, foam parties, and toga parties are the most popular. You'll be well aware of frat parties from the chalked announcements letting you know they're having another "non-alcoholic event." Other gatherings on campus are arranged by word of mouth and are usually smaller groups of friends hanging out. You can meet pretty cool people in small get-togethers.
Off campus, parties are bigger and wilder, and you are entirely at the whim of the Normal police. ISU has tenfold the number of parties Wesleyan has on any given weekend, and frats host only a fraction of the parties. While the accessible beverages, women, and general debauchery is greatly increased at ISU, the chance of getting a drinking ticket is almost inevitable. An undercover Normal police officer will walk right up to you, engage in a full conversation, and then slap cuffs. You won't see it coming. Of course, upperclassmen don't have this problem, and the bars in Downtown Bloomington offer refuge to thirsty souls in need of a drink. The bars attract different crowds, so you've got to check them out before frequenting any of them. They are as expensive as anywhere else, but Bloomington bartenders make stronger drinks than you get in Chicago.