Get Motivated: The Workout You Won't Cancel

• Consider personality. "Pick somebody who you really want to spend time with, because that's going to motivate you to go," says Stein. But don't convince your best friend to be your exercise buddy if she doesn't like physical activity. If you do, your plan could fail quickly.
• Make joint decisions. Find someone who shares your same exercise interests and whose schedule is similar to yours. Choose an activity location that's convenient for both of you.
• When possible, match skill levels. If you walk for exercise, your buddy's speed should be similar to yours. It's okay if she's a little bit faster, because that will encourage you to push yourself a bit. You don't want a wide difference in skill or you might feel as if you're holding her back. Matching ages doesn't matter, Brehm notes, as much as matching fitness levels. Partners of varying abilities can buddy up by meeting at a gym and using equipment set to their skill levels, such as elliptical trainers or treadmills.
• If you need extra encouragement, make an altruistic match. Some people have more success when they're exercising because it's good for someone else, such as an overweight child or a spouse with heart disease.
• Make your exercise sessions a priority. Buddies need a similar amount of commitment to the plan. "There have been many Saturday mornings," says Mosher, "when she shows up at my house at 6 a.m. and I say, 'If you weren't coming, I wouldn't be up.'"
• Have a back-up plan ready for when your buddy can't participate. Occasionally, your buddy will get sick or have a schedule conflict. If she can't make a session, have an alternate plan—whether it's to walk the same route alone or while talking to a friend on a cell phone, exercise to a DVD or video at home, or go to the gym. Knowing what you'll do will help keep you moving.
• Make adjustments when needed. Mosher and Stein have kept their buddy relationship active over the years by adapting to changes in jobs, family, and health. Success comes from "constantly tweaking what we're doing, to make it work for our lives," Stein says.

* The names of the exercise buddies in this article are pseudonyms.