By the time a meeting starts, most of what will happen in it has already been decided, by whoever wrote the agenda.
What the research actually found
Organizational psychologist Steven Rogelberg, drawing on more than two decades of research on meetings, found something most people have backwards. Simply having an agenda does almost nothing, the research shows little to no relationship between whether a meeting has one and how the people in it rate the meeting. The effect is entirely in what the agenda contains. What topics get included, what gets placed first, and who is explicitly assigned ownership of each item all measurably shape whether a meeting produces a real decision or dissolves into discussion without one. Rogelberg's own framing is blunt, a simple list of topics is a hollow crutch, an agenda only works when it is built around a specific goal for the time in the room.
Why this matters more than what gets said out loud
Two people can attend the exact same meeting and hold two very different amounts of influence over its outcome, not because of what either one said, but because one of them shaped what the meeting was structured to discuss in the first place. Whoever sets the sequence and the ownership has already made the more consequential decisions, the ones the room never actually gets to vote on directly.
Where to start
Before a meeting that matters, check who actually wrote the agenda. If it was not you, and the outcome matters to you, ask to add or resequence an item before the meeting starts, not once it is already underway.
Shaping the agenda is a quieter form of influence than speaking up in the room, and it is frequently the more decisive one.
Knowing exactly which item is worth pushing to add, and how much room you actually have to reshape someone else's agenda, is a judgment only you can make from inside your specific team. What this gives you is where the real leverage sits, before the meeting has even started.
There is a specific way to request a change to someone else's agenda so it reads as helpful rather than as taking over, and it is worth working out before the next meeting where the stakes are real.