Holding effective meetings (online or not) is a serious challenge for larger groups. Often, agendas are provided beforehand, but how does an agenda help and how does a good agenda look like?
Agenda = List of Decisions to Make
The heart of an agenda is the list of decisions, which should be made at a meeting. It is not about the timing of the event.
Use Agenda for Staying on Track
Most people recognize the agenda as a tool for the moderator to keep people on track. Often a discussion goes off topic or into too much detail. A good moderator will stop this and hinting at the agenda provides the necessary authority.
Use Agenda to Skip the Meeting
A big reason for the inefficiency of meetings is that so many people are wasting their time there, while it was not necessary for them to be involved at all. An agenda allows people to skip the meeting, if nothing of interest for them is found on the agenda.
Exact List of Decisions to Make
An important detail of agenda usage: It must be an exact list of decisions to make. All decisions to make must be on the list beforehand. Nothing more. Nothing less.
If not all decision are listed or new decision are added during the meeting, then the possibility to skip a meeting is gone. Many people will attend a meeting, just in case a decision affecting them might come up. This is a cultural issue, because people must trust the moderator to stick to the agenda.
Thanks jacques_chester for pointing this out to me