Mute your mic when you aren't talking.
Dress like you're going to the usual Meetup (in public).
Let us see you! Turn on your camera and use good lighting.
Definitely download the Zoom app (vs. web-only version) - you can use "Gallery View" to see everyone at once.
Do a "dry run" with your tech before showtime.
More useful Video Chat Etiquette from:
You can see a preview of what your camera will show by looking at the Video section of the Preferences in Zoom. It helps to see what everyone else will see (you, the room you're in, etc.) before joining the Meetup!
Below is an illustration of the difference lighting can make. On the left, only the room lights are on. On the right, a desk lamp has been turned on, behind the screen and camera:
Similarly, make sure the camera gets your whole face in frame, and try to avoid angles that make you look like Gulliver visiting the Lilliputians: