1. Learned, advanced devotees preach Krsna consciousness

    The best way to show mercy is to spread Krsna consciousness. The entire world is suffering for want of this knowledge. People should know that the Supreme Personality of Godhead is the original cause of everything. Knowing this, everyone should directly engage in His devotional service. Those who are actually learned, advanced in spiritual understanding, should preach Krsna consciousness all over the world so that people may take to it and make their lives successful. The devotee can do good not only to humanity but to all living entities as well. Everyone can benefit spiritually by the chanting of the Hare Krsna maha-mantra. When the transcendental vibration of Hare Krsna is sounded, even the trees, animals and insects benefit. Thus when one chants the Hare Krsna maha-mantra loudly, he actually shows mercy to all living entities.

    Srila Prabhupada, SB 4.31.19, ppt.