The first stage is initiation through a Mantra. Then in the second sage the student is given a concentration on a particular sound, light or Chakra along with the mantra. If the student achieves the successful completion of concentration on a Chakra (the centre of integration), the spiritual energy of that channel is awakened and blocked channels of subtle energy (Nadis, Nerves) are cleared. This initiation cannot be done by the student himself alone, but only through the initiatory powers of the Guru, his grace and blessings. The Guru is the channel of power flowing down the lineage of Gurus for a long time of thousands of years. Then student achieves many advanced stages of initiation, in sequence, until he achieves full realization of his own divine nature and God, through the grace and blessings of God.
In meditation when one-pointed-ness of mind is achieved, then like the continuous flow of oil from one vessel to the other, the concentration flows into meditation. The uninterrupted flow of the mind (Buddhi, Intellect) leads to timelessness, intuitive faculties awakened and divine knowledge dawns simultaneously. This process is possible only through the grace of Guru, without which one may lose in the murky maze of the subconscious, which is of diverse impressions and be unable to transcend the subconscious to attain the super-conscious state. Instead, in fact one may fall from the conscious to the subconscious rather than ascend from the conscious to the Super-Conscious and its purity and power.
Some of the concentrations, that when prescribed by a Guru lead to Super Conscious experiences are being explained, but they need be followed with the guidance of the Guru, as explained. Patanjali explains in 4th chapter of yogasutra, various methods of meditation. One of them is Mantra which means, "that which liberates the mind from all grief, sorrows and agonies." The Mantra is a secret teaching imparted by the Guru at the time of initiation. Mantra has one or more words chosen by the Guru as per the student leading him to the final truth. Mantras are not composed by the Guru, but have been handed down through the meditative tradition, having been revealed to Gurus and Seers while they were in a Super-Conscious state. The mantra is repeated throughout life as the same leads him to the stage of Samadhi.
JAPA and AJAPA:
Japa means chanting or the repetition of mantra or name. The japa of the Mantra also works on the level of the subconscious mind controlling moods and controlling undesirable emotional states like fear, phobias, greed, anger, frustration, lust, sloth and the like. A stage comes when the aspirant becomes AJAPA, the mantra reverberates with the subconscious and this aJapa is automatic. The Mantra purifies the mind making one capable of concentration necessary for his gradual evolution into super-conscious.
In the scriptures it is said that you get to meet the Guru when the disciple is ready. In yogic scriptures there are instances where many aspirants were initiated in their dreams by the great saints. The mantra received in such a dream experience is considered as sacred as those received in the waking state when the guru is at a great distance, or close by. Meditation in the dream experience, distant or intuitive experience is also one of the alternate methods of meditation.