Next to a strong will and determination, nothing is deadlier to your opponent than speed. Improve your speed by focusing your training on its two main components: force production and technique.
The most prominent styles being taught today are drive sprinting and reach-and-pull sprinting. Athletes who emphasize drive sprinting use their full potential of force production to gain speed and acceleration. With drive sprinting, the athlete will get his or her knees high before using a triple extension (ankle, knee, and hip) to drive into the ground. This projects the body across the ground with increased stride length. Drive sprinters also work to minimize "back action," in which the heel goes through the butt-kicking motion and the sprinter pulls the knee through, wasting valuable time in the hip cycle. Drive sprinters should do their best to efficiently bring the knee straight up and position the leg to drive into the ground.
An athlete's shin angle usually indicates whether he or she employs the drive or reach-and-pull technique. When the knee is high and in front of the ankle, the shin angle is positive. When the knee is behind the ankle joint, the athlete is over-striding and using reach-and-pull sprinting. Most hamstring injuries occur during simultaneous hip flexion and knee extension when the ankle is in front of the knee. This places the hip and knee in perfect position to pull a hamstring.
Since a good sprinter should be able to maintain acceleration mechanics for more than 40 yards, drive sprinting usually works better, since it emphasizes maintaining acceleration mechanics through the entire sprint.
In speed training, it's popular to teach speed maintenance. In this phase, the sprinter maintains his or her speed after reaching full acceleration. Since track and field sprinters run in a straight line for long distances, maintaining maximum speed after full acceleration is necessary. Most other sports require repeated bouts of re-acceleration mechanics due to body contact, acceleration, deceleration, or changing directions. For instance, a football receiver running down field is in contact with a defensive back the entire time; and whenever body contact breaks the stride, acceleration mechanics start over again. The only sprint components we need to teach—for effectiveness, time, efficiency, and simplicity—are acceleration mechanics and maintaining acceleration technique through an entire sprint.
Keeping the heel and toe up achieves minimum contact time with the ground and more muscle activation producing more force into the ground. A good technique for preventing is to sprint barefoot, because it naturally emphasizes the knee/toe/heel up, which activates many of the muscles often shut down by today's thick, soft running shoes.
Proper posture is essential to upper-body mechanics. Correct posture creates more force production and ensures the hips are going through the correct muscle firing sequence. The elbows should be at 90 degrees with the hands relaxed and moving from hip to back pocket. When you drive the elbow back at 90 degrees, you force the rear shoulder to transfer the good posture into the opposite glute for greater force production into the ground.
Combining correct technique with an effective program to increase force production will maximize results from your speed training. Good technique also correlates with a decrease in injuries by preventing over-striding.
For more on speed training, speed training drills, speed teaching progressions, and all aspects of sports performance, please check out my book, The Power Revolution.