Things I have learned from doing the nativity play and carol sings:
1. Make rehearsal CDs. Make them early. Have the track list on a USB drive in case anyone loses their copy of the CD. Make my *own* copy of the CD so that I don't need to keep borrowing classroom copies.
2. Learn to play the piano! My gosh, all of this would be *so* much easier if I could play the piano instead of relying on CDs (which keep getting lost/scratched/etc.) and/or hoping that Linda is available for rehearsals.
3. It is important to have the set lists early on so that we can see in what ways the songs need to be edited- is the key too high? Too low? Are the words too complicated? Are the words so simple that the tykes get bored singing halfway through the song and trail off before staring into space? This is good to know before the show!
4. Actions for every part of the song (don't leave one verse with the tykes just standing there because you couldn't think of a good action for "shepherds"). Simple is better. Reinforcing the lyrics is best. Sure, let the kids help out with the actions- but only one action per line- that's how it will end up anyway and doing too many just confuses the issue.
5. Sort out the choreography of leading- are the teachers doing everything? Am I doing everything? Either I need to get out of the way and the teachers need a chance to practice the whole group standing up bits or I need to know when each and every kid has their line so that I can cue and prompt when necessary. Again- figure this out early on! And ask the teachers what they would prefer! Having the classroom teachers totally on board is both polite and necessary.
That's what I've got off the top of my head right now, I'm sure there is more that I'm currently forgetting...