"Saint Pat's Day reminds me of Halloween," says Jack McGarry, a Dublin native and a bartender at the Dead Rabbit Grocery and Grog in New York City. "It's a good excuse to behave badly." With that in mind, Details asked some veteran barkeeps to describe what really happens on March 17 (that's Monday, folks) inside the bars they manage—and how good, decent boozers can escape the amateur-hour, green-beer goofballs. The esteemed experts include the aforementioned McGarry, Jamie Walsh of Stoddard's Food & Ale in Boston, and Doug Quinn of Hudson Malone in New York. Warning: Foul language ahead.