The Following is a very nice verse from the Sri Caitanya-caritamrta about the importance of Chanting the Holy Name of the Lord. Following that is the verse which describes the importance of chanting the names śrī-kṛṣṇa-caitanya prabhu-nityānanda before chanting the Hare Kṛṣṇa mahā-mantra, and the ten kinds of offenses which should be avoided.
…”Of the nine processes of devotional service, the most important is to always chant the holy name of the Lord. If one does so, avoiding the ten kinds of offenses, one very easily obtains the most valuable love of Godhead.” (Antya-lila 4.71)
Similarly, Śrīla Sanātana Gosvāmī has praised the chanting of the holy name as follows in his Bṛhad-bhāgavatāmṛta (Chapter One, verse 9)
“All glories, all glories to the all-blissful holy name of Śrī Kṛṣṇa, which causes the devotee to give up all conventional religious duties, meditation and worship. When somehow or other uttered even once by a living entity, the holy name awards him liberation. The holy name of Kṛṣṇa is the highest nectar. It is my very life and my only treasure.”
The Hare Krishna Movement 