Are external factors affecting you?

• Pain
• Equipment
• Players
• Crowd

 Maybe it's internal factors that are causing your lack of concentration?

• Are you hungry? Have a high protein or fruit snack. Have nourishing well-balanced meals Healthy diets earn higher grades. Eat a good protein rich breakfast. Avoid sugary snacks because varying blood sugar levels negatively affect concentration. High fat foods cause sluggishness and drowsiness. Snack on fresh fruits and vegetables.
• Are you tired? Have plenty of night-time sleep Fighting sleepiness lowers concentration; regular sleeping patterns improve concentration.
• Are you bored or dislike a particular subject? Read more about the subject and find reasons to interest you. 
• Does an assignment frighten you? Practice.  Break up large assignments into smaller pieces and do a little each day. Do the most intimidating part first. Give yourself rewards for progress. 
• Do you daydream? When your mind wanders, write down the interrupting thought and go back to the task at hand.  If you're on the field, do things that will bring you back into the game -- count the number of players on the field or focus on the ball (see below).  
• What if something is worrying you? Identify and define the problem and develop a concrete, specific plan to resolve it.
• Decide to concentrate We tend to do what we tell ourselves we can. 
• Prepare to concentrate Before you begin have everything you need on hand.  
• Increase the amount of time you concentrate for longer and longer Increase by a few minutes longer each session.
• Reward yourself. Decide on some activity you enjoy. Only allow yourself to do it after you have succeeded in concentrating.

• Practice Fatigue. If an athlete tends to lose focus when he is fatigued, he should arrange his practices so that he is fatigued. Then he must practice concentrating while being fatigued. If an athlete does not like being watched, he should practice while people watch. Most of all, athletes should approach practice as if it were the real thing. The game face should not be reserved for game day only.  Every time an athlete goes out onto the court, field, or ice she should go out there focused and ready to perform.

• Practice Distraction.  Practice with distractions surrounding you, and acclimate yourself in ignoring them. Fixating on external factors outside of your control (weather conditions, poor warm-up, or mistakes from prior contests) will disrupt your concentration coming into the contest at hand. Negative thoughts cost energy, creates anxiety, and serves as a distraction to your teammates.

• Use pre-performance routines. These can be very subtle or extremely elaborate. Routines help increase concentration and focus because they help block out both internal and external distractions. The consistency a routine provides also helps the athlete perform consistently.

• Use cues and triggers. These are effective tools in improving the ability to concentrate. Cues that are task-related help the athlete focus on  exactly what they are doing and keep them in the present. For example, a tennis player having trouble with her forehand might use the cue "follow through" to get back on track.

• Use key words.  Come up with a few key words to remind you on what you should be focusing on during the competition. These key words should also help with your visualization of the event as well. Visualization is one of the best training mechanisms to bring your mind and body together, and also helps you to focus on your everyday cares in your non-athletic life.

• Label.  Label what your doing 'thinking' just as prescribed in meditation.  Don't judge yourself.  Don't be angry to yourself for losing concentration.  Just label what you're doing 'thinking' and gently bring yourself back to the here and now.  Catching yourself doing this by labeling without judging will decrease the amount of times you lose focus and the length.

Want to improve concentration and reduce the chatter in your head.  Focus on the ball...intimately. 

Don't just look at the ball.  Concentrate on it...and not just the ball, the details of the ball.  Focus on the stitching of the football, the seam of the soccer ball, the ridges of the golf ball.  Which way is the ball rotating?  Where is the logo?  How quick is it moving?  You don't have to know the answer to these questions, but by focusing on the ball to the point of identifying the seams, you are, by default, concentrating on the play while stfifling the negative chatter in your head.