Regarding preaching work: If you simply reproduce verbatim the purports which I have given in the Srimad-Bhagavatam, and chant Hare Krishna with ecstasy, that will be sufficient for your preaching work, and as you do it seriously and sincerely, Krishna gives you more and more strength for this noble missionary work.

From Srila Prabhupada’s letter to Harivilasa — Montreal 10 June, 1968