In the beginning you can meditate twice daily, from 4 to 6 in the morning and 7 to 8 at night. As you advance in your practices you can increase the duration of each sitting little by little using your common-sense and discretion, and also have a third sitting either in the morning between 10 and 11 or in the evening between 4 and 5.
In the Yoga-Vasishtha you will find: "The right course to be adopted by one who is in his novitiate is this: Two parts of the mind must be filled with the objects of enjoyment, one part with philosophy and the remaining part with devotion to the teacher. Having advanced a little, he should fill one part of the mind with the objects of enjoyment, two parts with devotion to the teacher and remaining one with getting an insight into the meaning of philosophy. When one has attained proficiency, he should every day fill two parts of his mind with philosophy and supreme renunciation and remaining two parts with meditation and devoted service to the Guru. This will eventually lead you on to meditation for twenty-four hours."
Sitting in your favourite meditative pose and keeping the head and trunk erect, close your eyes and gently concentrate on either the tip of the nose or space between the two eyebrows or the heart-lotus of the crown of the head. When once you have selected one centre of concentration, stick to it till the last with leech-like tenacity. Never change it. Thus, if you have chosen to concentrate on the heart-lotus after having tried other centres, stick to the heart-lotus alone. Then only you can expect rapid advancement.
Meditation is of two kinds viz., Saguna (with Gunas or qualities) meditation, and Nirguna (without Gunas or qualities) meditation. Meditation on Lord Krishna, Lord Siva, Lord Rama or Lord Jesus is Saguna meditation. It is meditation with form and attributes. The Name of the Lord is also simultaneously repeated. This is the method of the Bhaktas. Meditation on the reality of the Self is Nirguna meditation. This is the method of the Vedantins. Meditation on Om, Soham, Sivoham, Aham Brahma Asmi and Tat Tvam Asi, is Nirguna meditation.
The wise cut asunder the knot of egoism by the sharp sword of constant meditation. Then dawns supreme knowledge of the Self or full illumination or Self-realisation. The liberated sage has neither doubt nor delusion. All bonds of Karma (action) are rent asunder. Therefore be ever engaged in meditation. This is the master-key to open the realms of Eternal Bliss. It may be disgusting and tiring in the beginning, because the mind will be running away from the point (Lakshya) every now and then. But after some time it will be focussed in the centre. You will be immersed in Divine Bliss.
When you get a flash of illumination, do not be frightened. It will be a new experience of immense joy. Do not turn back. Do not give up meditation. Do not stop there. You will have to advance still further. This is only a glimpse of truth. This is not the whole experience. This is not the highest realisation. This is only a new platform. Try to ascend further. Reach the Bhuma or the Infinite. Now alone you are proof against all temptations. You will drink deep the nectar of Immortality. This is the acme or final state. You can take eternal rest now. You need not meditate any further. This is the final goal.
You have within yourself tremendous powers and latent faculties of which you have really never had any conception. You must awaken these dormant powers and faculties by the practice of meditation and Yoga. You must develop your will and control your senses and mind. You must purify yourself and practise regular meditation. Then only you can become a Superman or God-man.
Every human being has within himself various potentialities and capacities. He is a magazine of power and knowledge. As he evolves he unfolds new powers, new faculties and new qualities. Now he can change his environment and influence others. He can subdue other minds. He can conquer internal and external nature. He can enter into superconscious state.
Just as the light is burning within the hurricane lamp, so also the Divine Flame is burning from time immemorial in the lamp of your heart. Close your eyes. Merge yourself within the Divine Flame. Plunge deep into the chambers of your heart. Meditate on this Divine Flame and become one with the Flame of God.
If the wick within the lamp is small, the light will also be small. If the wick is big, the light also will be powerful. Similarly if the Jiva (individual soul) is pure, if he practises meditation, the manifestation or expression of the Self will be powerful. He will radiate a big light. If he is unregenerate and impure, he will be like a burnt up charcoal. The bigger the wick, the greater the light. Likewise, the purer the soul, the greater the expression.
If the magnet is powerful, it will influence the iron filings even when they are placed at a distance. Even so, if the Yogi is an advanced person, he will have greater influence over the persons with whom he comes in contact. He can exert his influence on persons even when they live in distant places.
During meditation, note how long you can shut out all worldly thoughts. Watch your mind. If it is for twenty minutes, try to increase the period to thirty minutes and so on. Fill the mind with thoughts of God again and again.
"Though men should perform Tapas, standing on one leg for a period of 1,000 years, it will not, in the least, be equal to one-sixteenth part of Dhyana Yoga (meditation)."-Pingala Upanishad.
You must daily increase your Vairagya, meditation and Sattvic virtues such as patience, perseverance, mercy, love, forgiveness, etc. Vairagya and good qualities help meditation. Meditation increases the Sattvic qualities.
Considerable changes take place in the mind, brain and nervous system by the practice of meditation. New nerve-currents, new vibrations, new avenues, new grooves, new cells and new channels are formed. The whole mind and the nervous system are remodelled. You will have a new heart, a new mind, new sensations, new feelings, new mode of thinking and acting and a new view of the universe (as God in manifestation).
During meditation you will get into rapture or ecstasy. It is of five kinds viz., the lesser thrill, momentary rapture, flooding rapture, transporting rapture, and all-pervading rapture. The lesser thrill will raise the hair of the body (like the goose-skin). The momentary rapture is like the productions of lightning moment by moment. Like waves breaking on the seashore, the flooding rapture descends rapidly on the body and breaks. Transporting rapture is strong and lift the body up to the extent of launching it into the air. When the all-pervading rapture arises, the whole body is completely surcharged and blown like a full bladder.
"Whatever he (the Yogic practitioner) sees with his eyes, let him consider as Atman. Whatever he hears with his ears, let him consider as Atman. Whatever he smells with his nose, let him consider as Atman. Whatever he tastes with his tongue, let him consider as Atman. Whatever the Yogi touches with his skin, let him consider as Atman. The Yogi should thus unwearied gratify his organs of sense for a period of one Yama (3 hours) every day with great effort. Various wonderful powers are attained by the Yogi, such as clairvoyance, clairaudience, ability to transport himself to great distances within a moment, great power of speech, ability to take any form, ability to become invisible, and the transmutation of iron into gold, when the former is smeared over with his excretion."-Yogatattva Upanishad.
Leading a virtuous life is not by itself sufficient for God-realisation. Concentration of mind is absolutely necessary. A good virtuous life only prepares the mind as a fit instrument for concentration and meditation that eventually lead to Self-realisation or God-realisation.