Any athlete worth the sodium chloride dripping in water droplets down his well-toned body will tell you that sprinting is about two things and two things alone: speed and power. However, those two things can be furthered divided into even more qualities and subtle nuances. If you're interested in learning how to sprint effectively, you should take careful note. Sprinting is not just a matter of having massive legs; it is in fact a skill and a sport.
Two other important qualities, which make up the "power" aspect of the power/speed duo, are posture and balance. Having a correctly aligned spine is vital to effective running, and walking for long distances can correctly align the spine. Try alternating between jogging, walking, and sprinting. Walk for a few miles to warm up, stretch your muscles and get the blood flowing first of all. After your body is in the proper mood and metabolic rate, sharply sprint for a hundred meters or so, and then slow down to a jog for a little bit until you're back at a walking pace. Repeat this several times and you will not only have better posture, but you will also have increased your endurance seven-fold.
One of the best things you can do to increase all aspects of your sprinting ability is to train not your muscles, but rather your lungs. Learn to breathe deeply and slowly, using your solar plexus to push air into the extremities of your lungs. This will supply your entire muscular system with the much needed oxygen, and thus fuel, it needs to keep pumping your legs and arms at an accelerated pace. Try deep breathing first as a meditation practice without moving, and then try it while walking, jogging, and then full-on sprinting. This should help greatly.
Although it may at first seem counter intuitive to the untrained mind, it is in fact extremely important in such refined and hard-to-master skills such as sprinting to put forth absolutely no effort. To be more specific, the type of speed you want is the kind that you can summon up without trying, something that is completely natural to you. If you have to strain to move as fast as you want, your body is not functioning at its maximum capacity. Thus, proper training will turn your turtles-and-the-hare like races into the sublime performance of a master sprinter. Using the basic tools and ideas provided coupled with diligent practice should have you become an effective sprinter in no time.