Om is the original Word of Power, or "mantra." A mantra is a series of verbal sounds whose effect lies not in an assigned intellectual meaning, as is the character of common language, but which possesses an inherent sound-power that can produce a particular effect, physically or psychologically--much in the way that music can produce such effects, though not as profoundly. The word mantra itself comes from the Sanskrit expression manat trayate, which means "a transforming thought;" literally: "that which when thought carries across"-that is, which produces an objective, perceptible change. It also literally means "a liberating thought."
Sound and consciousness are, practically speaking, the same. And the master yogis of India have through the ages stated that God and Om are ONE. That is, the infinite Consciousness of God is inherent in the syllable Om. Since the individual spirit and God are essentially one (though not the same), we can tentatively conclude that Om, repeated within the mind in japa and meditation, will both produce the consciousness of God and the restoration of our union with God.
The Practice of Om Yoga Meditation
1) Sit upright, comfortable and relaxed, with your hands on your knees or thighs or resting, one on the other, in your lap.
2) Breathe naturally. Your mouth should be closed so that all breathing is done through the nose. This aids in quieting the mind. Though your mouth is closed, the jaw muscles should be relaxed so the upper and lower teeth are not clenched or touching one another, but parted.
3) Turn your eyes somewhat downward and close them gently. This removes visual distractions and reduces your brain-wave activity by about seventy-five percent, thus helping to calm the mind.
4) Now begin intoning Om over and over again, like the tolling of a resonant bell, "singing" It on a single note. Make sure the O and the M get approximately "equal time"-Ooomm. (Not Ommm or Ooom.) Don't torture yourself about this--approximately equal is good enough. It is, however, essential that your intonations should be continuous and not broken up. That is, there should be so separation or break between your intonations. Rather they should be continuous, forming a single stream of sound: OoommOoommOoommOoomm; not Ooomm. Ooomm. Ooomm. Ooomm. When a bell is tolled, the sound of the previous stroke is still vibrating when the next one occurs. It is the same with our intonations of Om. This is important.
5) Keep on intoning Om in an unbroken stream at the rate that seems most comfortable or "right" to you at the moment--quickly, moderately, or slowly. Whatever you feel to do at the moment is right, and it is just fine to change back at forth during your meditation. Your deep intuition is coming into play, and as you are a living organism, so also will your intoning of Om be living, and therefore sometimes change in speed of repetition.
6) Do not let your intonations of Om get caught or captured by any physical process such as the breath or the heartbeat, as this draws you into body awareness and the limitations of the subconscious, and can even put you to sleep! Japa must be an act of will, of the free impulse that rises from deep within, from the Self. Doing japa in time with the breath or heartbeat develops passivity and integration with the material side of our being rather than the spirit. This is extremely important to understand.
7) Simply intone Om inwardly, "listening to" or "hearing" the mental sound of your intonations of Om. Your intonations should be resonant and strong. You do not shout or bellow inwardly, but you do intone in a robust or full-bodied manner with no hesitation or feebleness. Experience Om as both cause (inner speaking) and effect (inner hearing) in a relaxed and easeful manner, experiencing the inner sensations produced by this practice. This enables you to enter effortlessly into the Witness Consciousness that is your finite spirit within the Infinite Spirit that is God.