Preparing your body for soccer is a process that is often overlooked, especially at the lower levels of the game. There are three main aspects that must be touched upon in order to achieve maximum physiological readiness.

Circulation - Picking up the Metabolic Rate
Passive
Before jumping into a competitive event, the body's cardio-vascular activity needs to be increased gradually. Up to 30 minutes before kickoff, it is recommended to drink tea (preferably with a lemon and sweetened by honey rather than sugar.) The tea contains caffeine, which will increase a player's heart rate. Tea is rich in Sodium, a mineral that regulates and balances the amount of fluids outside the cells in the body, aiding in muscle contraction and nerve function. Sodium is usually lost during endurance events like soccer in the means of sweat.
Prior to going out to the field, light massage should be applied to the poorly circulated parts of the body like the ankles, knees, lower back and shoulders. This is especially important in cold weather.

Active
The active warm-up must begin about 20-30 minutes before the actual event. During this process, the body has to be warmed up through active exercises such as light jogging. The intensity should be gradually picked up. Incorporating different muscle groups at this stage will uniformly warm up the body.

Musculature - Stretching
Stretching is misunderstood and misused by many coaches at the lower levels of the game. First off, it must never be used on "cold muscles." Unless you're body has been warmed up, stretching can only cause harm. Remember that it should never feel painful. Flexibility is influenced by genetic factors. The same result cannot be expected for two different players when it comes to stretching.

Static
Static stretches are done by gradually assuming a position and holding it for a period of time. The only advantage of using Static stretches before a game is that they will ease sore muscles and calm down the player. It is true that they also improve flexibility but only when used in a long-term program.

Ballistic
Dynamic or Ballistic stretches involve moving a specific joint in full-range from one extreme to the other. It has been shown that Ballistic stretching decreases a risk factor for injury called muscle stiffness. Muscle stiffness is the ratio between change in muscle resistance and the change in muscle length. Static stretches have no effect on muscle stiffness. Therefore, stretches, done before soccer games or practices, need to be Ballistic. Nearly all established teams address only Ballistic stretches in their pre-game routine and go right into a technical workout.

Coordination - Technical-specific Workout
The final step before kickoff is the technical warm-up. At this point, the body should be well warmed up. Ideally, the technical warm-up should incorporate all four major areas of skill including kicking, dribbling, ball control and tackling. In fact, many teams conduct a "compressed" technical practice just before they actually play. They start off with simple technical drills and build up to a small-sided possession game.

Resources used:
European Approach to the Warm-up in Soccer by Prof. Angel Spassov, Ph.D., D.Sc.
Conditioning for Soccer by Joe Luxbacher

Strength Training for Soccer

There is a common misconception about strength training and soccer. Traditionally, soccer players did not employ it, due to the fear of getting too big and thus losing their agility. The opposite has been proven and nowadays nearly all top soccer players (both male and female) incorporate strength training in their fitness routine. It must also must be emphasized that building up your muscles is a long process that will not produce drastic results. Possessing a well-developed body can improve performance in many ways. For example, 50-50 battles are usually won by the stronger or more aggressive player. Another advantage is that strength training can help with muscle imbalance. Muscle imbalance causes alterations in your running technique that can potentially lead to injury.
Muscle strength is developed through the use of heavy weights, which allow only a low number of repetitions. To achieve optimal gain, try to keep the period between repetition short. When working with lighter weights and doing a higher number of repetitions, one can improve the tone of his/her muscles. If you are just starting a weight-training program, it is recommended to tone up your muscles before trying to build up muscle mass.
The use of training equipment such as exercising machines and free weights is helpful but is not imperative. It is possible to improve your muscle strength by using the weight of your own body for resistance. The most important factors for a successful training regiment are the effort and dedication you put in.

Significance for the soccer player:
-having a poorly developed body causes injuries
-it usually makes you less effective in 50-50 battles
-it degrades your muscle endurance

Speed and Soccer Training

Throughout his development, a player's sprinting ability is acquired mostly during early puberty (between 12 to 14 years of age.) If you already are a grown player (over 16 years old) and your timing on 100 meters is 15.0 seconds, it is not going to improve very easily. However, it is possible to significantly enhance one's speed on the field through a number of methods, which do not involve sprinting.
There are many factors that influence the speed at which one performs on the field. Some of these include reflexes, tactical anticipation, agility and so on. An effective speed training program must incorporate realistic aspects from the game. Speed is not confined to sprinting alone. Soccer players rarely sprint for over 20 meters. It would be more appropriate to concentrate on rapid change of direction, acceleration and most importantly, speed with the ball. Keep in mind these ideas when designing your speed training program.
Fatigue renders speed training useless in terms of gaining additional pace. A well-designed workout should be spilt into intervals so that you can recover and exercise at maximum effort.

Significance for the soccer player:
-playing at high speed is increasingly important at the more competitive levels of the game
-if you don't have the adequate pace, you will have trouble getting the ball.