I would like to preface this by saying I am not an excellent conductor. I am decent, but that's all the credit that I will give to myself.
Because I majored in a music program in college and have continued in music through my career, I have been able to see many other conductors at work. Some are amazing, and some were average. Honestly, none were outright terrible!
All conductors have their own styles, and choirs gradually learn to adjust to each style that is presented. However, there is one key technique that all excellent choir directors have a tendency to do. I try to do this as much as possible when I conduct, and I have noticed an improvement in my choir's singing each time I emphasize this technique.
What is the technique?
Breathing before directing the choir into a line of the song.
The biggest issue is that many directors cue their choirs right on the choir's starting note. If a director is doing that, then it's too late! The choir won't come in until a half a beat later, meaning that the beginning of the line is already missed.
The first step is to make sure you're looking at the choir at every entrance. I'm not always the best at this, so I try to memorize my music - or at least the complicated entrances. If you're looking down at the music then the choir is going to understand that you're unsure about the music and they'll reflect that feeling.
The second step is to pretend that you're singing the song. If you were singing the song, you would take a solid breath in the beat before the line begins. Your breathing - and don't be minimal about it - make sure your choir sees you take a breath! - needs to be confident and solid. The choir will take the breath right with you. And if they don't, practice breathing together. Once you have confidence, they will have confidence.
Keep this technique in mind, practice it, and the choir will respond in a very positive way!