The fitness craze is going gangbusters, with gym attendance up 23% since 2001, to 41.3 million, according to the International Health, Racquet & Sportsclub Association (IHRSA). Most new recruits sign up in January, the busiest month for fitness clubs. That's when well-intentioned souls trying to stick to their New Year's resolutions flood their local gyms, often resulting in long lines at the treadmills, overtaxed gym staffs and towel shortages in the locker rooms. But it's not long before the throngs thin; most people who make those resolutions trip up in the first 90 days, says Alan Marlatt, the director of the Addictive Behaviors Research Center at the University of Washington. Indeed, that's what clubs expect. "They bet on it," says Meg Jordan, the editor of American Fitness magazine, adding that most gyms count on a 20% to 30% dropout rate. In the meantime, there are ways to avoid the January crowds and make it past the 90-day hump. When selecting a gym, visit the facility during the time of day you're most likely to attend. If it's crowded, check to see whether waiting lists and time limits on machines are enforced or whether it's a free-for-all.