Be still, and know that I am God - Psalms 46, the Bible
Yoga is the hindering of the modifications of the mind - Yoga Sutras of Patanjali
In an earlier article I discussed bare attention, the process in which you simply observe your surroundings without thinking of them. As an exercise bare attention serves to "cleanse the doors of perception" as Aldous Huxley said.
Bare attention is a form of meditation. The two quotes above illustrate another form of meditation, which I will call emptiness meditation.
In emptiness meditation the object is to empty the mind of all thought while maintaining full consciousness. Mind you, I don't say full awareness, because if done properly eventually you will lose awareness of your surroundings and your body, while remaining fully conscious.
The technique of emptiness meditation is simple. Sit down, preferable with your eyes closed and your spine straight. You can lie down, too, but it is easy to fall asleep this way, especially when you first start practicing. Then - don't think.
Though the technique is simple, the execution is not. You will experience thought. When you do, tell yourself, "That's okay", then let the thought go. The secret is to not hold on to the thoughts that do happen. An Indian analogy compares the mind to a monkey. It is always active, whether to a purpose or not. This form of meditation is like giving the monkey a sedative. You do not try to forcibly stop thought. But neither do you let yourself become attached to the thoughts that arise.
Practice this exercise for 10 - 15 minutes a day. This may not seem like a long time, but when you are practicing it is, and will lead to more benefits than trying to practice for two or three hours a day on a sporadic basis.
The benefits of this meditation include an increased sense of serenity and relaxation. Any form of meditation, and this one in particular, is almost a specific for decreasing psychological and physical stress. With the decrease in stress there is often as decrease in physical and psychological illness. You may also receive insight into beliefs that underlie your world view in the form of the thoughts that you see pass by as you sit with your mind empty. Put these aside for evaluation later when you aren't meditating. They can be valuable in helping you build a more helpful set of beliefs to underpin your world view. In the best of cases, you begin to live the quotes with which I started this article. You glimpse the source from which you come, and become acquainted with the deeper parts of your self.
In a minority of cases you shouldn't do this type of meditation. If it leaves you feeling more tense, or less in contact with the world, or more depressed, I would avoid it. Again, this happens in a small minority of instances. For most people, emptiness meditation is a great tool to use in developing your sense of inner peace and your ability to contact the deeper parts of your self.