Workouts designed to improve your speed for soccer should not be dedicated solely to sprinting. Your workout must resemble realistic game aspects like change of direction, acceleration and speed with the ball. Drills designed to improve speed need to be executed at maximum effort. They need to be segmented into intervals in order to suppress fatigue.

Technique

Off ball
Sprinting, in contrast to jogging, requires that you contact the ground with your toes. Your upper body should be slightly bent slightly forward. You must keep your arms aside of your body. Put emphasis on how you drive yourself forward with each step. By feeling out the ideal length of your stride, you can adjust for optimal performance. Once you have adapted a good sprinting stride, you should not change the rhythm by shortening or lengthening your step.
Mixed sprints of "slow motion running" and top speed bursts are a good way to get a feel for your technique. This will give insight whether you are marking superfluous motions while at top speed.
You can practice your ideal stride by placing a line of cones with an equal distance between each. When you sprint next to the cones they will give you a sense of the consistency in your stride and speed. Remember to swing your arms parallel to your path rather than across the body. This preserves energy. It is all about developing economical technique.

On ball
Generally, when a player is moving with the ball at speed, he has to keep a low center of gravity. The knees have to be bent. He has to be leaning slightly forward. When dribbling in a straight line, the ball has to be pushed with the instep and should not spin.
Control is extremely important when working on your speed with the ball. If you feel that you are losing your handle on the ball, you are moving faster than your skill level is allowing you.

Drills for speed

Warming up
Warming up the body must be done ahead of every practice that involves running at top speed. Ideally, you should spend 5-15 minutes trying to incorporate as many muscle groups as possible through light jogging, running sideways, backwards and so on.
It is very important to also warm up dynamically. It decreases muscle stiffness, which lowers the chance of injury incidents. Start with jogging while bringing your heels as back, as if trying to kick your own backside. This will loosen up your hamstring. For the quad muscle, jog while bringing your knees up as high as you can. Do not lean backwards. The calf muscle can be warmed up by jogging and periodically leaping up off of either foot. Remember to gradually increase the intensity of your warm-up.

Maximum speed
Set up a line of three cones. The first two will be the actual distance you are sprinting. The last one exists for practical reasons. Usually, when sprinting from one cone to the other people tend to slow down for the last few meters. By predefining the actual path for deceleration you can get preserve the quality of your sprint. Fatigue is not acceptable when working on this drill. If you are not sprinting at maximum speed you will not achieve the desired improvement. Work on sprinting drills, such as this one, early in your practice.

Acceleration
Put four cones in a line so that they split your path in three equal sections. Start from the first and gradually increase your pace until you reach the third cone. From that point on, sprint at top speed until the last cone. With each repetition, try to remain consistent when accelerating.

Weightlifting
Weightlifting is definitely a great way to build up the muscle tissue on your legs as well as your entire body. It must be emphasized that muscles built through weightlifting will not make your legs move quicker, they'll give you more power.
Benefits: Building your leg muscles gives you more power. The extra power can enhance your kicking, jumping and explosive speed. Having well-developed musculature also decreases the likelihood of injury. Good rest is vital for developing your legs. Muscles regenerate during the day after the actual exercise. Therefore, working out should not be done more than 2-3 times per week.

Plyometrics
Plyometrics is another training method suitable for developing your legs. It basically consists of jumping exercises designed to improve the responsiveness of your leg muscles.