The general instructions cover the following:
Feedback & echo audio
Zoom does have an in-built echo removal. But sometimes this does not remove the high-pitched feedback that can occur between your microphone and speakers. Therefore, have a tested pair of headphones available.
Zoom provide a test meeting: https://zoom.us/test
If you have not used Zoom before on your current PC setup, please visit the zoom test meeting and check that everything works.
Dress as if in a physical meeting; from head to toe.
Don’t use a distracting background within Zoom. These are alot of fun for a social event, but can be distracting for presenters and other attendees.
Body language while on a webcam
A good article on body language while being viewed on a webcam: