Q. Why do devotees in ISKCON greet each other with a ‘Hari Bol’ or ‘Hare Krishna’?

A. There are nine processes of devotional service namely hearing, chanting, remembering the Lord, offering prayers etc. Of these nine, Lord Chaitanya Mahaprabhu advised all devotees to accept chanting of Lord’s names constantly as the easiest means of deliverance in this age of Kali.
Therefore when we chant Hari Bol we are helping each other by reminding each other of this urgent neccesity to chant Krishna’s names.

We can say either Hari Bol or Hare Krishna whenever we want, either during happiness or distress, either during success or failure. There is no certain time when we should remember Krishna because we are supposed to remember Krishna always. So whenever you can, please chant Hare Krishna or Hari Bol. Lord Chaitanya Mahaprabhu and His associates personally chanted Hari Bol in great ecstacy.