Concentrate gently either on the lotus of the heart (Anahata Chakra) or on the space between the two eyebrows (Ajna Chakra or Trikuti), or on the tip of the nose. Close your eyes.
The seat of the mind is Ajna Chakra. The mind can be controlled easily if you concentrate on the Trikuti.
Bhaktas should concentrate on the heart. Yogis and Vedantins should concentrate on Ajna Chakra.
Crown of the head (Sahasrara) is another seat for concentration. Some Vedantins concentrate here. Some Yogis concentrate on the tip of the nose (Nasikagra Drishti).
Stick to one centre of concentration. Cling to it tenaciously. If you concentrate on the heart stick to it. Never change it. Guru will select a centre for concentration, if you are a student of faith. If you are a man of self-reliance, you can select a centre for yourself.
Bhrumadhya-Drishti is fixing one's eyes between the eyebrows. This region is Ajna Chakra. Sit in Padmasana or Siddhasana in your meditation room and practise this gaze gently from half a minute to half an hour. There must not be the least violence in this practice. Gradually increase the period. This Yogic Kriya removes Vikshepa or the tossing of mind and develops concentration. Lord Krishna prescribes this practice in chapter V, Sloka 27: "Sparsan kritva bahir bahyan chakshus-chaivantare bhruvoh"-"Having the outward contacts excluded and with gaze fixed between the eyebrows." This is known as 'frontal gaze,' because the eyes are directed towards the frontal bone or the bone of the forehead. You can select yourself either this gaze or the 'Nasal Gaze.'
'Nasal Gaze' is called Nasikagra-Drishti. The gaze is fixed at the tip of the nose. Even when you walk in the street, keep the nasal gaze. Lord Krishna prescribes this in chapter VI, Sloka 13: "Samprekshya Nasikagram"-"Looking fixedly at the point of the nose without looking around." This practice steadies the mind and develops the power of concentration.
A Raja Yogi concentrates on the Trikuti (Ajna Chakra, the space between the two eyebrows) which is the seat of the mind in the waking state. You can easily control the mind if you can concentrate on this region. Light is seen during concentration in this region very quickly even in a day's practice, by some persons. He who wants to meditate on Virat and he who wants to help the world should select this region for his concentration. A Bhakta or a devotee should concentrate on the heart, the seat of emotion and feeling. He who concentrates on the heart gets great Ananda. He who wants to get Ananda should concentrate on the heart.
A Hatha Yogi fixes his mind on the Sushumna Nadi, the middle path in the spinal canal, and on a specific centre, viz., the Muladhara or Manipura or Ajna Chakra. Some Yogis ignore the lower Chakras and fix their mind on the Ajna Chakra only. Their theory is that by controlling the Ajna Chakra all the lower Chakras can be automatically controlled. When you concentrate on a Chakra, a thread-like connection is formed in the beginning between the mind and the Chakra (centre of spiritual energy). Then the Yogi ascends along the Sushumna from Chakra to Chakra. The ascent is made gradually by patient efforts. Even a mere shaking of the opening of the Sushumna causes a great deal of Ananda (bliss). You become intoxicated. You will entirely forget the world. When the opening of the Sushumna is shaken a bit, the Kula Kunadalini Sakti tries to enter Sushumna. Great Vairagya comes in. You will become fearless. You will behold various visions. You will witness the splendid Antarjyotis. This is termed "Unmani Avastha." You will get different Siddhis, different types of Ananda and different kinds of knowledge by controlling and operating on different Chakras: If you have conquered the Muladhara Chakra, you have conquered the earthplane already. If you have conquered the Manipura Chakra, you have conquered fire. Fire will not burn you. Panchadharana (five kinds of Dharana) will help you to conquer the five elements. Learn them under a Guru who is an adept Yogi.