All of us have had situations in which we have attended meetings. I've attended more than my share and conducted more than my share of them. There are some basic considerations to keep in mind.

Each person in the meeting should have a specific task or a reason for being there and everybody in the meeting should know the task and mandate for everybody else. That should also be presented in writing to each participant beforehand. It's another way for you to assert control.

If two people work together on a task then neither one has any responsibility or authority and each one can effectively blame the other. Therefore, it is important to clarify which one is in charge although two people can attend a meeting with similar responsibility, as long as everyone knows which is the contact person, which is the one who is going to be in charge.