The subject of meditation is a vast one that cannot be covered adequately on a site like this, but we can have a go anyway. There are, of course, many forms of meditation and different approaches to the subject, so I will narrow the field down a little. Some people might not agree with my ideas on meditation, but this is inevitable. There are some vastly different ideas on the subject.
Most people with any experience in the field would probably agree that meditation normally involves a focusing of the mind in one way or another. So, as a starting point, we could perhaps say that meditation is a way of focusing without thinking. I say "without thinking" because meditation must necessarily be different from thinking; otherwise, we might just as well think. Correct? (This is not to say that thinking has no place; after all, I must do some thinking to put this page together.)
So, in meditation, we are trying to focus the mind in a particular way, which is different from thinking. This is perhaps the key to the subject: we are interested in using the mind in a way that is different from the usual thought processes that dribble through our minds incessantly throughout the day. This tends to lead to the inevitable questions: how do we meditate and why do we meditate?
There are many reasons for meditating. At the very least, we can meditate for the sake of our health and wellbeing. Clinical research has shown that meditation lowers blood pressure and stress, creates relaxation and enhances alertness. Some research has shown that long-term meditators tend to be physiologically younger than their actual age. The British researcher Max Cade has demonstrated, with his Mind Mirror, that meditation creates a perfect balance between the two hemispheres of the brain, and this appears to affect health.
This is the most basic reason for meditating, but naturally we can go a lot further. Meditation can open up vast areas of psychic and spiritual experience, which is not so easy to demonstrate in a laboratory, but which is nevertheless very real. However, by its nature, it can only be understood through experiencing it; not by thinking about it, talking about it or reading about it. It is essentially experiential.
Meditation plays some part in most religions, not to mention the psychic fields like mediumship, spiritual healing and any number of New Age activities. In studying the major religions -- particularly those from the East -- one can find extremely detailed descriptions of spiritual experiences that seem to go hand in hand with meditation. There is a whole literature on the subject of mysticism, which is concerned essentially with developing a closer relationship with this thing we call God. Even Christianity, which could not be called a mystical religion, has its share of mystics. The Spanish mystic, St Teresa of Avila, produced a book in which she divided the spiritual path -- or contemplative life -- into seven stages. The first three were the confused, unclear stages, when our mystic had no clear sense of direction and frequently not the faintest idea what was going on. In the fourth stage, there was a breakthrough and things became clearer; the aspirant knew what he/she was doing, knew what direction to go in and would usually adopt some form of prayer or meditation as a way of going deeper.
In the fifth stage, there would be a major breakthrough and the mystic would actually start to experience a sense of union with God. This would be followed later by a major period of purgation, during which the aspirant would feel an agonising sense of being cut off from God. This painful purgation would eventually lead to the seventh stage: union with God. Another Spanish mystic, St John of the Cross, called the sixth stage the Dark Night of the Soul, and described it in great detail in a book of the same name.
All the major religions have their mystics, but some religions are more mystical than others. The main religions that could be called mystical religions are Hinduism, Buddhism and Taoism. Christianity, Judaism and Islam are not mystical religions; their mysticism is more at the periphery, rather than the centre. The Indian religions have gone into mysticism in great depth; most of the mystical influences that have seeped into the western world over the last few decades originated in India, with some influences from Taoism and Zen Buddhism (the popular New Age talk about "going with the flow" originally came from Taoism).
No matter what religion or philosophy was involved, sooner or later there would be some form of meditation that was used to go deeper. Christian mystics mostly tended to focus on God, while the Indians developed many forms of spiritual practice. These are generally described as a form of yoga, which means yoke or union; once again, union with God, or at any rate a spiritual practice that was aimed at union with God. In the west, we usually think of yoga as a lot of elaborate exercises, which is known as Hatha Yoga. There are, however, many yogas. There is Bhakti Yoga, which is the Yoga of love and devotion; this is similar to what was practised by Teresa and John of the Cross. There is also Mantra Yoga, Laya Yoga, Jnana Yoga, Raja Yoga, Karma Yoga and Siddha Yoga. Some form of meditation was always part of the discipline.
It is impossible to treat all these things in detail, so I will outline a basic introduction to some of the main aspects and forms of meditation.
I do not practise yoga and have always been sceptical about the "text book" approach to meditation, but have found from experience that posture does indeed make a difference. You can feel the energy flowing better if you sit up straight, compared to slouching around. Whether sitting crosslegged or in a chair, it is worth giving the spine a good stretch and lifting the chin a little to straighten the neck. You will notice that you feel quite different from the way you feel if you slouch. Try a little experiment: sit sloppily, with your chin on the palm of one hand. Take note of how you feel. Then sit up perfectly straight, with the spine stretched out, your chin lifted a little and your hands clasped in your lap. How do you feel now? You will notice that you feel completely differently from the way you felt when you were slouching. In the latter position, it is impossible to feel the same way you feel when you are up straight.
On one occasion, I tried sitting up very erect on a lounge, with my head tilted back, but without trying to meditate in any way at all. After a while, I could feel a sensation like energy rising in me. Eventually, the sensation was so strong that I decided to stop because the energy would keep me awake. Sure enough, when I went to bed, the energy stopped me from getting to sleep; something indeed happened, and all I did was sit up straight.
Sometimes you will see people sitting for meditation with their hands held in a certain way: with thumb and index finger touching each other and the palms facing upwards. This is called chin mudra and is said to keep the meditation energy in the body. Personally, I have always found it distracting, so I prefer to have the hands clasped comfortably in my lap, which is just as good.
II. The Breath
In most forms of meditation, some awareness of breath is cultivated. Some people, in fact, treat this as a form of meditation in its own right. As such, it is probably the most basic from of meditation, but is not very powerful on its own. For most practical purposes, we plebs only have to concern ourselves with making sure the breath is natural and relaxed. It is not necessary to engage in forms of deep breathing.
After assuming a relaxed but straight posture, with your eyes closed, become aware of your breathing. Take note of the breath going into your nostrils, then feel it go into your chest. Then feel the stomach muscles expand naturally as you breathe in. Make sure they are completely relaxed and you are not trying to force them to do anything. They will expand naturally as you breathe in because the diaphragm tightens, which pushes the stomach out. In this relaxed state, you are ready for whatever meditation you want to do.
Mantras are Sanskrit words or phrases which are used in meditation for various purposes. There is a vast number of them and they can be used for many reasons: pure spiritual growth, healing, prosperity, enhancing relationships and many other things. Many of them take the form of a plea or expression of devotion to a particular god, either out of pure spiritual devotion or, sometimes, a desire for help with a problem. They are normally repeated steadily for a particular time; for most of us, a minimum of twenty minutes is normal. This may be done once daily, or more if you have the energy.
Mantra repetition is known as japa. It is usually done in the sitting position, but can also be used in other ways. For example, it can be done while walking, which is known as a walking japa. In my experience, silent repetition is the most effective, but mantras are sometimes chanted out aloud.
Many mantras start with the word Om (also spelled AUM). This word has no translation, but is said to be the primordial sound that was present at the creation of the universe. All sounds, including other mantras, are said to derive from Om. It can be used on its own for meditation, or in combination with other words.
Many mantras also use the word Namah or Namaha, which means, roughly, to honour someone or express salutations to them. This is common practice when the mantra is addressed to a god. One example is the mantra Om Namah Shivaya, which means "Om, I honour Shiva." There are many other examples (see the Mantras section for more detail).
Mantras are sometimes synchronised with the breathing, but not always. If used on its own, Om must always be synchronised with the breath, and is only used on the inbreath (see Mantra section). So Ham is another mantra that must be synchronised with the breathing: "So" on the inbreath and "Ham" on the outbreath.
Visualisation is a very powerful form of meditation and can be used for many purposes. One can visualise a god or guru as a pure spiritual practice; do various kinds of visualisation to cultivate clairvoyance; do "creative visualisation" to attain goals; visualise people and ask them questions.
Visualisation can also be used for spiritual healing. One method is to visualise a ray of golden light going into someone (some people prefer white light). This is often used to augment a session of hands-on healing, in which the healer might give direct healing through a series of hand positions, while at the same time visualising golden or white light light going into the person (other colours also have their uses, but this is beyond the scope of this site). Long-distance healing can be done on someone by visualising them looking healthy and happy, possibly doing things they might normally find difficult. You could also surround them with white or golden light if you have the energy (visualisation can sometimes be rather taxing). It can also be used to give yourself healing by visualising the light going into any part of your body needs healing.
I have found that visualisation tends to be conducive to getting messages and information through mental pictures, which is clairvoyance. For this reason, it may not entirely appeal to the spiritual purists who are concerned with nothing but spiritual growth, and who understand that psychic abilities have nothing to do with spirituality and may in fact be an impediment to it.
Whether you are one of those purists or not is entirely your business. If you are interested in developing clairvoyance, visualisation will help.
Mindfulness is the general cultivation of awareness as a daily practice in one's life, which means awareness of one's own thoughts and feelings as well as the surrounding world. It is practised a great deal in various Buddhist schools, especially Vipassana. There are Vipassana centres that hold courses in which people are completely silent for ten days, during which they spend their time cultivating mindfulness, or awareness. Most people who do these courses are enthusiastic about them, although some find them too regimented.
Another version of mindfulness is found in the teachings of the great spiritual iconoclast, J.Krishnamurti, who refined his approach over the years until it was based on pure awareness and nothing else, with not the slightest trace of a belief of any kind, religious or otherwise. I practised Krishnamurti's approach for seven years, until I came to the conclusion that it was unnecessarily harsh, dry and cold. The spiritual path can be hard enough without people like Krishnamurti making it even harder. A certain degree of self-awareness is virtually inevitable with meditation, because it tends to make one more self-aware. However, to practise self-observation and nothing else as a way of life -- as one's whole approach to life -- tends to lead to self-absorption, as well as being unnecessarily dry and cold. After seven years of this approach, I moved on to other things; Krishnamurti's approach, as far as I am concerned, has nothing to recommend it.