These are two videos of a choir that I work with in Orange County. In each of them you can see some standard choir directing moves that I use all the time, as well as some signaling that is specific to the particular song.
(By the way, this choir has excellent musicians who play on almost all of their songs. It's just a coincidence that both of these videos are a cappella songs.)
On this song, King Jesus Is A-Listenin', most of the gestures you see are my standard moves. The way that I'm following the rhythm of the singing and the notes going up and down with my hands, I always do that.
But on the lines where the sopranos say, "He's got power in His hand, and He's taking me away," you'll see a gesture that I improvised for this song. I hold out one hand in the direction of the sopranos, with my palm facing toward them (the first time it comes is at the 1:24 mark). The reason for the gesture is that during rehearsals the sopranos were sometimes singing the word as "hands", a plural, when it's supposed to be singular, "hand." So I started showing them my single hand as they sing that line to remind them not to put an "s" at the end of "hand."
Something else that didn't show up in the video is when they reach the part that says "oh, oh, oh, oh, King Jesus is a-listenin'", I formed "O"s with my hands to let them know we were going to that section of the song.
Now here's another video of the same choir (different day and different person doing the filming, so it's a little rough):
This song is called "Hallelujah Lord."
Here, as we're starting into the song (at the 0:12 mark), you can see me doing the classical-style conducting beat patterns. That wasn't necessary at the beginning of "King Jesus Is A-Listening" because the beat isn't as strict on that song, you can be flexible with it. But on "Hallelujah Lord" everyone is singing different rhythmic lines that have to fit together, so it's very important to stay on a steady beat. The tenors are the ones who anchor the song, and I counted off two measures for them so that they would have a strong sense of the tempo before they started.
When the altos come in (at 0:31), you see me gesture toward them with two fingers outstretched. This is because they start with a split part, first altos and second altos singing different notes. They always remembered this anyway, but it doesn't hurt to give a signal that's in sync with them.
At 0:36, there's a phrase where the tenors sing one line while the other parts sing a different one on top of it. I start the tenors off because they come in first, but then for the rest of the phrase all of my conducting is synced with the other three parts. That's because the tenors were the most solid on their part. I knew that I could leave them to carry theirs on their own and focus on the others. If the tenors had been at all shaky about keeping to their rhythm, then I would have had to practice conducting their line with one hand and the line for the other parts with the other hand (that would have taken a lot of preparation and practice, but it is possible).
At 1:21, they start into another passage where several different lines are going on. The tenors start off, then the second altos, then the sopranos, then the first altos. At 1:38, the basses join in. Once they come in, my conducting is completely focused on the basses. It had been a challenge for them to hold onto their timing and their notes in this passage during rehearsals, so I give them full attention to help them stay on track.
One of the beautiful things about rehearsal time is that you can observe your choir and see what areas they need the most support in. A director who knows their choir can work on guiding them through songs in the way that is best for them, a way that a stranger wouldn't be able to do, no matter how skilled the stranger may be. Sort of like John 10:27.