When it comes to cardio, HIIT (High Intensity Interval Training) is the best way to strip body fat without losing muscle. Innumerable studies have found that practicing HIIT reduces body fat quicker and more effectively than steady state cardio. I always start with a three minute warm up, and then alternate between intense and moderate cardio on the treadmill with small rest periods. To get the most out of your HIIT workout, do not spend more than three minutes at a high intensity, and do not spend more than two minutes on a rest period.
You'll see below that I alternate between walking (rest), running (intense), and walking at an incline (moderate-intense). The pink numbers reflect the moderate and intense exercise, and the black represents rest. I do this workout four days per week after weight lifting, and I change up my HIIT routine ever so slightly every once in awhile to avoid muscle memory. This can involve just one extra incline level, or a quicker MPH while I run.