harer nāma harer nāma
harer nāmaiva kevalam
kalau nāsty eva nāsty eva
nāsty eva gatir anyathā
In this Age of Kali there is no other means, no other means, no other means for self-realization than chanting the holy name, chanting the holy name, chanting the holy name of Lord Hari.
[Adi 17.21]
…
This hari-kīrtana was started five hundred years ago in Bengal by Lord Caitanya. In Bengal there is competition between the Vaiṣṇavas and the śāktas. The śāktas have introduced a certain type of kīrtana called kālī-kīrtana. But in the Vedic scriptures there is no recommendation of kālī-kīrtana. Kīrtana means hari-kīrtana. One cannot say, “Oh, you are Vaiṣṇava. You can perform hari-kīrtana. I shall perform śiva-kīrtana or devī-kīrtana or gaṇeśa-kīrtana.” No. The Vedic scriptures do not authorize any kīrtana other than hari-kīrtana. Kīrtana means hari-kīrtana, the glorification of Kṛṣṇa.
So this process of hari-kīrtana is very simple: Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. Actually there are only three words: Hare, Kṛṣṇa, and Rāma. But they are very nicely arranged for chanting so that everyone can take the mantra and chant Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare. Since we have started this movement in the Western countries, Europeans, Americans, Africans, Egyptians, and Japanese are all chanting. There is no difficulty. They are chanting very gladly, and they are getting the results. What is the difficulty? We are distributing this chanting free of charge, and it is very simple. Simply by chanting, one can have self-realization, God realization, and when there is God realization, then nature realization is included also. (from The Science of Self Realization)
The Hare Krishna Movement 