Worse are meeting with just a vague title and not a well defined agenda. So many times I have to ask the organizer to add bullet points of the items to cover so I can at least join already prepared, can tell the organizer if I am not really the right person to join for the meeting and/or if someone from another team would be necessary.

So many time is wasted on meeting because of off topic stuff or because the rights persons haven't been invited.