Tips to improve concentration

1. Concentrate without physical tension. Many new meditators, in an effort to concentrate more deeply, tense the muscles in their body. Deep concentration, however, is possible only in a state of relaxation.
2. Relax your body. To concentrate effectively, you need to start by relaxing the body. A very effective way to release stored-up bodily tension is to inhale and tense the whole body, and then release the tension as you exhale. Yogananda recommended tensing and relaxing, as well as the Regular Breathing Technique before meditation.
3. Pray before you meditate. This will help you remember why you are meditating! You will also be inviting the Divine, or your Higher Self, to help you in your practice.
4. Sit perfectly still. Moving your body the slightest amount sends energy, or life-force, into the muscles. Since the purpose of yoga is to draw your energy inward, any physical movement reduces your effort because it draws your energy and awareness into the body. To keep yourself from fidgeting during meditation, try thinking of your body as a rock — solid and unmoving.
5. Sit longer. Your restlessness will subside the longer you sit in meditation. Even a glass of muddy water becomes clear in time, if the water is allowed to sit undisturbed.
6. Keep your eyes gently raised. The point between the eyebrows, or spiritual eye, is the seat of concentration in the body, and whenever we need to concentrate deeply, we naturally focus there. It is very beneficial to keep the eyes lifted, without strain, during meditation. If you do, you will notice an improvement in your concentration.
7. Consciously withdraw the energy from the body. Practice the Hong-Sau Meditation Technique; it is one of the most sacred techniques of yoga because of its ability to interiorize and focus the mind.
8. To develop concentration, do one thing at a time, and do it well. Practicing concentration in daily life will help you concentrate better during meditation.
9. Concentrate with interest. When you really want something, it is difficult notto think about it! Concentrate with interest on whatever you do, and you will find yourself absorbed in it.
10. Pray for concentration and devotion. Sincerity means having the support of one’s whole being. Pray for sincerity of effort in your meditation practice!

Source: http://www.ananda.org/meditation/free-meditation-support/articles/10-tips-to-improve-your-concentration-in-meditation/