Mute the sound so as not to be heard by others unless agreed upon otherwise by all participants.
Sit you own sit, come and go freely on your own time.
Do not sit Zazen facing directly toward the computer screen or camera, turn your back to the computer, or at least show a side profile, and face the wall instead.
Gassho when joining or leaving. If you're not facing the screen, or otherwise not being able to view the screen, it's optional to gassho back. ##Or is it always optional to gassho back?##
The person who opens the hangout (who is first) might ring a bell at start and end of the sit, IF (!) not otherwise agreed