I'm not a choral conductor by training, but I've had a few innings on the podium.
In 1994 and 1995, I got a wonderful opportunity to participate with some very august company in conducting the Messiah Sing at St. Mark's Church in Mt. Kisco, NY. The first year, one of the other conductors had to point out to me that you gesture the penultimate beat of a 4/4 or 3/4 bar on the outswing, not the inswing. Oh well.
I'll never forget this: I started my first Messiah sing by briefing the assembled singers that I liked to take my assigned chorus a bit faster than they're used to, "just watch me and you'll be fine," I said. Right. Every nose immediately became buried in the score and it was like dragging a truck tire through molasses!
My scariest moment onstage was in 1993 when I took up the baton to conduct my singing group, Serious Fun, at SUNY Theater A in Purchase, NY. This was a Philharmonia Virtuosi Christmas concert playing to a packed house (maybe 2,000). Dick Kapp, the conductor of the orchestra (not to mention the whole orchestra) was right behind my back (snickering, no doubt) as I attemped to lead my group in a rhythmically tortuous song called "Jing!". Thanks to a bunch of great singers, we pulled it off without a hitch.