I would like to know what preposition ‘meeting’ should take. Should I say I’m at a meeting or I’m in a meeting?
In my opinion the difference lies in actively and passively participating.
In a meeting means you are actively participating in the meeting.
"I'm busy right now. I'm in a meeting."
At a meeting means you are present at a meeting but not necessarily participating.
"When you are at a meeting you have to talk quietly when taking a phone call."