Select the correct microphone for choir use. A cardioid condenser microphone is preferable since it is unidirectional and will provide a rich, warm sound.
Determine the number of microphones you need. A general rule is that one microphone is needed for every 16 singers. Don't use more than necessary, since interference between the microphones can be a problem. Professional choirs usually require three microphones spaced about three times the distance between the sound source and the first mic.
Attach the microphones to rafters or metal rods placed high above the singers, and adjust the height so that each microphone is approximately 2 feet above the heads of the back-row singers. This will allow the sound of the entire choir to travel without overemphasizing any one singer.
Place the microphones in front of the choir approximately 3 feet from the front row of singers and 1/3 of the way in from the sides of the choir. Make sure to follow the rule that mics should be spaced three times the distance between the source of the sound and the mic. For this setup, the mics should be 9 feet apart.