If you want the extra edge in sports, having a higher vertical is key. The difference between high school and college and the professional level can be a few inches in vertical leap. Here is how you can improve your explosiveness for sprinting or sports that require jumping.
Stretch out before and after a workout, and also before you jump. Stretching is important because it prepares your muscles for activity, reduces the risk of injury, and prevents soreness. From a jumping perspective, stretching actually improves your vertical. It allows your leg muscles to contract and expand more than if you don't stretch, thus increasing your ability to jump higher. Think of your legs as coils. The more you stretch, the more you can coil your legs up to explode more.
Lift weights. Not only should you be squatting, working your hamstrings and calves, but you should be developing upper body strength too. Develop your shoulders, biceps, back, chest, and abs. The upper body plays a huge part in your vertical and having a stronger one will let you jump higher. Just try jumping without moving your arms and keeping your back upright and you'll see what I mean.
Jump after you fatigue your muscles. For example, do a wall sit where you sit with your back against the wall and your legs bent until your legs burn and you can't do it anymore. Immediately after, do a set of box jumps. When your quads are already fatigued, it is the best time to jump because you get more out of it.
On box jumps, practice quickness. When you jump up on the box, get off and as soon as you land, jump back up again. You should do these in sets of 12 and do about 2-3 sets per workout. As you continue to improve, move up the height until you get to about 3 feet. You can go further if you are able to.
Before and after a workout, do wall jumps. These are when you face a wall and jump as high as you can in order to touch the ceiling or some other bar. You can do this moving down a wall, walking a few paces down after each landing or you can do them in place. Do about 30 before and after.