Meetings sometimes lead away from the origin topic and results in detail discussions about themes which do not belong to the actual content of the meeting. As moderator you have to preserve the participants before drifting into such discussions. There are the following effective steps which will help you to keep the discussion topic in mind.
Name the topic and explain the goals of the discussion
You should do this within the invitation and at the start of the discussion.
Create an Agenda
You should create a small Agenda with the main milestones of the meeting. This is usefull, especially if you want discuss different topics. Add the Agenda to the invitation and also show it at the beginning of the Meeting.
Keep the topic in mind
Whenever the participants discuss about other topics you can lead them back to the origin theme. For example you may stop a discussion with: „Yeah, that’s an open point; we will discuss it separately.“ or just ask „Does this belong to our topic today?”.