From the Atmajyoti website:
The three elements of Om Yoga meditation
There are three components of Om Yoga meditation: 1) sitting with the eyes turned up and then closed; 2) being aware of our breath as it moves in and out, and 3) mentally intoning Om in time with the breathing and listening to those mental intonations. They are the essential ingredients of Om Yoga meditation, and we should confine our attention to them. If in meditation we feel unsure as to whether things are going right, we need only check to see if these three things are being done and our attention is centered in them. If so, all is well. If not, it is a simple matter to return to them and make everything right.
Of the three, listening to the mental intonations of Om is the major key to success in meditation. It is essential that we become centered in the etheric levels of our being, from which sound arises, and this is done by inwardly intoning Om and listening to those intonations. During meditation, whatever happens, whatever comes or goes, relax and keep listening to your inner intonations of Om. It is the sound of Om that accomplishes everything. And by listening to It you become totally receptive and responsive to It so It can work Its transforming purpose to the maximum degree.