A workout buddy is hugely helpful for keeping motivated, but it's important to find someone who will inspire—not discourage. So make a list of all your exercise-loving friends, then see who fits this criteria, says Andrew Kastor, an ASICS running coach: Can your pal meet to exercise on a regular basis? Is she supportive (not disparaging) of your goals? And last, will your bud be able to keep up with you or even push your limits in key workouts? If you've got someone that fits all three, make that phone call.