We’re not saying you need to tell a potential trainer to rip off his shirt and show off his six-pack before you hire him, but let’s be honest. He should appear pretty fit. “The very best trainers are the ones who live, eat, sleep and breathe health and fitness,” Duffy says. Plus, you won’t be inspired to get in the best shape of your life by someone with a gut, right? And as Duffy puts it: “If you’re going to climb Mt. Everest, are you going to go with a guide who has been there numerous times—or someone who read a book on how you get there?” Enough said.