But Wait! The Warm Up
Warming up is not a widely practiced routine. You know you should do it; but chances are you don't, or at best, I used to grudgingly spend a token minute or two throwing myself around a little.
Warming up does not mean stretching cold muscles. Confusing stretching and warming up is common, but dangerous practice. Warming up can mean pretty much any moderate exercise that raises the pulse gradually. The purpose is also to raise the body temperature and psychologically prepare. That warmer temperature increases the elasticity of muscle, thus reducing the risk of ripping or straining it. It also increases the metabolic rate of cells and the readiness of the nervous system.
As a beginner, your warm up is already built in the system with the walk/run program. As you progress, you may want to start your running routine with a walk and then a gradual pace increase.