A big presentation is only as good as the message it delivers. Once you know what you want that message to be, you need to create the right supporting content to reinforce it. Start by sitting alone with a blank piece of paper. After you’ve done some initial brainstorming on your own, bring together a group to help clarify your argument. Encourage them to put half-baked or embarrassing ideas out there. Treat every idea as valuable. Have someone facilitate and record the ideas so the discussion can move quickly. If it slows down, people will start to question and censor themselves. Take the seeds of ideas that came from the rapid-fire group session and then do another round of quiet brainstorming on your own to further hone ideas.
Adapted from the HBR Guide to Persuasive Presentations.