Take regular exercise.
Brain takes its nutrients from blood for functioning properly. Physical exercise speeds up blood circulation to brain and brain gets well nourished as well as brain gets rid of waste products. Physical exercise is necessary for enhancing power of concentration.
Study in a place with no or less distractions.
Your study place should be free from such things which may absorb your attention, i.e television, music, changing color bulbs, maps etc. Similarly study in quiet place free from sound distractions.