Visualization helps you to create a strong, vivid memory. Try to picture in your mind what you wish to remember. Try to remember a man's name for example, by seeing his face in your mind and associating his name with it. People often say that they can't concentrate or that they will never be able to learn to concentrate better. Quite often it is our way of life that takes away our former ability in this area.
Small children are well skilled in concentration.
Concentration can be defined as focusing attention on one thing and to one thing only. When you do an exercise which provides an opportunity for you to do this, it is basically an exercise in concentration. Visualizing will help. Visualizing forces attention to one thing only. If you try to see specific pictures as you read, it will help you to concentrate.