Regarding prasadam, leftovers should always be taken if they have not spoiled or if they have not been touched by diseased persons. We should never waste Krishna prasadam. Best thing is to cook only what is required and then give each person what he wants. That is the Vedic system, that the people sit in rows behind their plates and servers pass down the rows and put a very small portion of each foodstuff on each plate, unless there is some objection by a person then nothing is given. Then if anyone wants more, the servers pass up and down the rows continually and give more if anyone requests. In this way nothing is wasted and everyone is satisfied.
Letter to Kirtiraja das, 27 November, 1971