The criterion is that a devotee must know what Krsna wants him to do. This can be achieved through the medium of the spiritual master who is a bona fide representative of Krsna. Srila Rupa Gosvami advises, adau gurv-asrayam. One who is serious in wanting to render pure devotional service to the Lord must take shelter of the spiritual master who comes in the disciplic succession from Krsna. Evam parampara-praptam imam rajarsayo viduh. Without accepting a bona fide spiritual master coming in the disciplic succession, one cannot find out the real purpose of devotional service. Therefore one has to accept the shelter of a bona fide spiritual master and agree to be directed by him. The first business of a pure devotee is to satisfy his spiritual master, whose only business is to spread Krsna consciousness. Yasya prasadad bhagavat-prasadah: if one can satisfy the spiritual master, Krsna is automatically satisfied. This is the success of devotional service. This is the meaning of the word anukulyena-that is, favorable devotional service to the Lord. A pure devotee has no plans other than those for the Lord's service. He is not interested in attaining success in mundane activities. He simply wants success in the progress of devotional service. For a devotee, there cannot be worship of others or demigod worship. A pure devotee does not engage himself in such pseudo-devotional service. He is interested only in satisfying Krsna. If one lives only for the satisfaction of Krsna, he does not have to accept this order or that order. One's only business should be to satisfy Krsna. This process is completely manifest in the activities of the Krsna consciousness movement. It has been actually proved that the entire world can accept devotional service without failure. One simply has to follow the instructions of the representative of Krsna.