Reading through the book The a-z of visual ideas, I came across this tip: do not hesitate to make a fool of yourself in a creative briefing. So true. I think the largest part of my contribution as a presentation designer is asking the stupid questions, and having the courage to take a fresh perspective on things.
If you design your own presentation, ask a friend or colleague to take the role of asking the stupid questions. If you are working in a big corporation and need to design a presentation for a senior executive, maybe try to get a few minutes of 1-on-1 time to ask the stupid questions, it easier to make a fool of yourself there then in a huge meeting.