Taking the Next Step(s)

• Increase your weekly mileage. Set goals, if that helps. Shoot for 20 miles per week, or more. If you have more time on weekends or a certain day of the week, try a longer walk of 4-6 miles or more. One caution: don't increase your weekly mileage by too much all at once. Most experts recommend no more than a 10% increase per week.
• Add cross training to your exercise regimen. It brings variety to your workout plans, and keeps you from being bored or feeling like you're in a rut. Biking and swimming are good options, because they're cardiovascular exercise (they get your heart rate up), but use different muscles than walking. Strength training is another possibility. Using weights or resistance training helps you build muscle, which means you burns more calories and fat, even when you're resting. 
• Consider entering a race. A local 5K is a great place to start. The goal here isn't to win the race. Instead, it's about getting out and showing off your healthy lifestyle, and enjoying being part of an active community.
• Step up your pace. Wear a watch and time yourself on your favorite routes. Try to beat your previous time.
• Keep a fitness and exercise journal. Track your daily and weekly mileage, other forms of exercise, how you felt, new things you tried. Looking over what you've done in the past can be good inspiration for future things to try or try again.
• Add intervals to your walking workout. Start out with fartleks: pick an object like a street sign or a driveway, and walk as fast as you can to that point, then resume your normal walking pace; repeat. Next try intervals: walk fast for 1 minute, then slower for 2 minutes. Work your way up to 2 minutes fast, 1 minute slow.
• Try using a heart rate monitor. This will allow you to target your exercise near your maximum heart rate, to make sure you're making the most of your workout.