1. Think incline.
Climb anything you can (like stairs and parking-garage ramps) and you'll burn up to 50 percent more calories than you would on level ground. If you're on a treadmill, start with a 5 percent grade, then work up to 7 or 8 percent — where you'll really feel the intensity. Avoid holding handrails, which lessens the difficulty of your workout.
2. Increase your speed.
If you can walk at a pace of about 4.7 mph, you'll burn as many calories per mile as you do when running. Do intervals (go as fast as you can for 30 to 60 seconds, then move at a more moderate speed for five minutes) to prevent fatigue and keep your metabolism revved long after your walk.
3. Pump your arms.
Bend your elbows at a 90-degree angle and swing from your shoulders like a pendulum. Keep the movement short — if you reach out too far in front, you won't be able to move them as fast to burn maximum calories.
4. Invest in walking poles.
Join the Scandinavians in the trend of Nordic walking, or moving ski-like poles in a dynamic forward and backward motion. (Find more info at anwa.us.) Sure, you might get some stares from the neighbors, but you'll be burning 20 to 45 percent more calories.
Looking for a specific treadmill walking routine to try? Check out this 20-minute cardio challenge workout: