I just got back from a very relaxing choir retreat yesterday evening. Our Cantor presented to us that morning the "five pillars of good singing." It wasn't until a few hours ago that I recognized the play on words. But anyway - here they are:
* Posture: envision your hip bones as the center of your body, rather than letting your heels bear all the weight and letting your clavicles be dragged down.
* Breathing: use the breath you take! Oxygen is the chorister's best friend. Try to open your throat when you take a breath (and use your belly, not your chest! This allows deeper inhalations) so you won't sound like you're drowning.
* Konsonants (yep, with a "k"): spit these out, as they add energy to your singing. (We sopranos never win the consonant award; the tenors always do because they have my similarly-trained brother in the front of the section.)
* Vowels: there are five pure ones (ah, eh, ee, aw, ooh) and diphthongs (combinations of these - for example: "I" = ah-ee).
* Listening: you are not the only one singing! Listen to your section members and also to the choir as a whole. This will help the choir stay in tune with each other, if not with the starting key (those pesky a cappella pieces!). Rule of thumb: Don't sing so loud that you can't hear your neighbor. If your voice sounds unnaturally breathy, you may be singing into your folder. Don't.
These five pillars apply to any choir; the sixth one, applying to only Christian ones, is to have Jesus in your singing. A favorite quote: "Be Jesus with skin on."