OM (Pranava) is a ferry-boat for men who have fallen into the never-ending ocean of mundane life. Many have crossed this ocean of Samsara with the help of this ferry-boat. You can also do so if you will meditate constantly on OM with Bhava and meaning and realise the Self.
OM is the only symbol for the Immortal, All-pervading Self or Atman. Think of OM to the exclusion of everything else. Shut out all mundane thoughts. They may again and again recur. Again and again generate thoughts of the pure Self. Associate ideas of purity, perfection, freedom, knowledge, immortality, eternity, infinity, etc., with OM. Repeat OM mentally.
Om is everything. Om is the name or symbol of God, Isvara or Brahman. OM is your real name. OM covers all the threefold experiences of man. OM stands for all the phenomenal worlds. From OM this sense-universe has been projected. The world exists in OM and dissolves in OM (AUM). "A" represents the physical plane, "U" represents the mental plane and astral planes, the world of spirits, all heavens, "M" represents the deep sleep state, and all that is unknown even in your wakeful state, all that is beyond the reach of the intellect. Om represents all. OM is the basis of your life, thought and intelligence.
All words which denote the objects are centred in OM. Hence the world has come from OM, rests in OM and dissolves in OM.
OM is the symbol of Brahman or the Supreme Being. Meditate on OM. When you think or meditate on OM, you will have to think of Brahman, the thing signified by the symbol.
Association with OM is to become one with the thing signified. "Tad-japas-tadartha-bhavanam." Try to identify yourself with the All-blissful Self when you think or meditate or chant OM and negate the five Kosas as illusory adjuncts created by Maya. You have to take the symbol OM as Sat-Chit-Ananda Brahman or Atman. This is the meaning. During meditation, you should feel that you are all purity, all light, all-pervading existence, etc. Meditate on the Self daily. Think you are different from mind and body. Feel "I am Sat-Chit-Ananda Atman-I am all-pervading consciousness." This is the Vedantic meditation.
Meditate on OM till you attain Samadhi. If your mind gets distracted by Rajas and Tamas, practise Dharana (concentration) and Dhyana (meditation) again and again.
"Having made one's body or the lower self, the lower fire-stick, and Pranava (OM) the upper, by the friction of continued practice (Abhyasa) of meditation one should see God (Atman) hidden within." -Svetasvatara Upanishad.
O Rama, you are now living in the Himalayas. Be in tune with the Nature's Lord. The lofty peaks will whisper to you the secret of life eternal. The gurgling streams around you will sing the song of Omkara to you. Fix your mind in Pranava-Dhvani and enter into sublime communion easily. Nature will reveal to you her closely guarded secrets. Take lessons from her. Feel your unity or oneness with the snow-clad peaks, the glaciers, the refreshing Himalayan breeze, the rays of the sun, the blue sky, the glittering stars, etc.
May you all rest in the non-dual Brahman and taste the nectar of immortality. May you all reach the fourth state of bliss (Turiya) by analysing the experiences of the waking, dream and deep sleep states. May you all have a comprehensive understanding of Omkara or Pranava and the Amatra. May you all enter the soundless OM by transcending the sounds A, U and M. May you all meditate on OM and attain the goal of life, the ultimate Reality, Sat-Chit-Ananda Brahman. May this OM guide you. May this OM be your centre, ideal and goal. May the secret and truth of Mandukya Upanishand be upon you all, OM OM OM!!