You walk without think about the movements of your legs, feet, arms and hands. You just do it. And you just grab your running shoes and start running. But, as there is a correct way of running, press the pause button right now for a restart.
Do it the correct way:
Step 1: Stand up straight, or at least as upright as you do when you walk. Contract your stomach muscles, especially those below your belly button, as if you don't want the skin of your stomach to touch your running shorts.
Step 3: Contract your buttocks and tuck your butt in.
Step 4: Start running, but try to keep your body as stable as possible. Let your arms swing close to your body. All your movements should aim for energy conservation - no big swaying of the shoulders, upper body or hips. Just your legs, and arms moving easily from your stable core.
Don't take huge strides, for this will automatically tilt your pelvis forward, leading to an arched back and strain on your hamstrings. You want your stomach muscles taut, your shoulders back and your bum tucked in.