First of all God's work must benefit other people.
I abide in all beings as their inner-most soul. Disregarding My
presence within them, men make a show of worshiping Me through images.
If one disregards Me present in all as their soul and Lord but
ignorantly offers worship only to images, such worship is as
ineffective as a sacrificial offering made in ashes. A man who
persecutes Me residing in others, who is proud and haughty, who looks
upon God as the other – such a person will never attain to peace of
mind. If a man disregards and persecutes fellow beings, but worships
Me in images with numerous rituals and rich offerings, I am not at all
pleased with him for proffering such worship. A man should, however,
worship Me in images, side by side with discharging his duties, which
include the love of all beings, until he actually realises My presence
in in himself and in all beings. As long as man is self-centred and
makes an absolute distinction between himself and others (without
recognising the unity of all in Me, the Inner Pervader), he will be
subject to the great fear of Death (including every form of
deprivation of self-interest). So overcoming the separateness of a
self-centred life, one should serve all beings with gifts, honour and
love, recognising that such service is really being rendered to Me who
reside in all beings as their innermost soul.
Srimad Bhagavata Purana III.29.21-27
Secondly, he must identify with other people's interests.
O Arjuna! In My view that Yogi is the best who, out of a sense of
identity with others on account of the perception of the same Atman in
all, feels their joy and suffering as his own.
Finally, a person who does God's work must also not make the mistake that his work is really helping other persons, that he is saving people. He should do his best but he must keep in mind that only Ishvara can really help others.
Therefore, O dear one! Give up your infatuation born of ignorance,
which makes you feel worried, thinking – how will these helpless
people get without me? To think that one can save or protect another
while one’s own body, subject to the power of time, karma and Guna, is
decaying, is like a person in the grip of a python thinking of saving
Srimad Bhagavata Purana I.13.44-45