QUESTION: I have a scene in a restaurant where staff is coming and going. How do I describe that? Do I mention all the movement?
This is really about viewpoint. You are describing the scene from your viewpoint character's perspective. What will she see?
Imagine this. You are in your favorite romantic restaurant. Across from you is your special someone or your favorite sexy actor. You are eating your meal, flirting, and talking. Would you be aware of who is coming in and out of the room?
Your character in a similar situation would do the same thing.
Imagine this. You are in that restaurant with that sexy lover, but someone wants to kill you.
You would be very aware of who is coming and going in the room, and so would your viewpoint character.
If it's a situation that's emotionally neutral like a banquet meal with servants coming and going to bring food, you can say something like "A steady stream of servants, each with a large tray of food or an empty bowl, moved through the room tending the tables.”
Then, unless there's a reason to mention the servants again, or a servant again, you don't mention them. The reader will fill in the visual blanks.