Relax the upper body
If you watch all the top sprinters and you will notice how relaxed their upper bodies are, how their facial muscles and hands are almost floppy. This is because when a player tenses any of his upper body muscles his whole body tenses, which will slow him down. A good tip is to get your players to sprint with open hands and relaxed neck and shoulders.
Balls of the feet
To get the full power out of the legs of the players, they need to sprint on the balls of their feet. Demonstrate this to the players by getting them to try running on the heels and on flat feet. Then have them run on the balls of the feet and feel the difference.
Use ankle flick exercises in your warm-ups to develop strength and power in the ankle and lower leg.
The higher the knee lift, the more power is generated when the foot returns to hit the ground. Work hard on high knee lift drills in your warm-up.
Your legs move at the same speed as your arms. Get your players to jog on the spot with their arms by their sides. Then tell them to pump their arms as fast as possible and notice what happens to their legs. They will move much faster.
In order to sprint efficiently the elbow joint needs to be locked at 90° and the arms need to drive backwards explosively on each step.
Develop arm power with players sitting with outstretched legs. They drive their arms and try to get their backsides off the ground.
When in full flight it is important to get the hips or pelvis are tilted forward (think of Michael Johnson running). This makes sure the gluteus muscles (your backsides and the largest in the body) are used properly when sprinting. It also helps the player stay balanced when sprinting as their feet stay underneath their body.
Game related wprints
As well as technique, you will need to work on game-specific sprint skills. Sprinting with a ball is very important and players need to work on acceleration, changes of pace and changes of direction at speed. Also think about the different distances players sprint in a game and make some of your training drills position specific.