1) Stand with your feet at shoulder width. Your arm position is of personal choice. You can either mimic a running motion with them or hold them in front of your body bent at the elbow and your palms facing downward (acting as pads for your knees)
2) Lift your left knee towards your chest.
3) Bring your left leg down and lift your right knee towards your chest.
4) Alternate your legs in a fluid motion at a running pace.