Try to run quietly, and you’ll find that you rise up on your toes a bit, shorten your stride, and gain better control of your body. Ninjas move quietly. Try running like a ninja to improve your running economy.
One of the most difficult things to learn as a distance runner is to shorten your stride and focus on quick steps to minimize injury. If you shorten your stride and focus on a quicker turnover you’ll be lighter on your feet and run longer with less effort. This is most apparent on hills.