Preparing for presentations is really hard. This may not be news, but it is a very tough part of the process. And just like in lots of experience design work, you may be judged solely by your deliverable and not necessarily any of the work put in to it.
But making something genuinely good, something one can be proud of, is a challenging adventure.
When I know I need to give a presentation I start by understanding the audience. Who will be there? Why am I there? What information are they expecting from me, and what are the most important things they need to remember from my presentation?
If this sounds a little like a stakeholder or user interview, well, you're not far off. It needn't be that formal but doing just enough research into who you're speaking with is essential.
Next I consider format. I'd like to steer myself toward content, solely, at this point but I really enjoy exploring what is needed. Given the information and the audience, will this be a pretty in-depth thing? Where and when can I be myself? Is there anything unexpected that could work? How much time do I have?
One thing I definitely stick to is the old saw of, "Tell them what you're going to say, say it, and then tell them again." This works. Use it.
Content tends to come next. That's when I bust open Drafts or TextWrangler and make outlines. I refine the outline and flesh out the story. I've tried two approaches to outlines: totally in-depth and just bullet points. Bullet points work better for me.
As soon as I have something written and in my head, I begin to practice. I find a quiet room, bring my iPhone, and record it. I listen to it and time it. I make notes on what I notice, what's clunky, what's brilliant, and to the speed and pacing.
I then revise and practice again. If I can practice in the actual space I'll be speaking, I do it. This helps me get a real feel for the room and how much I'll need to worry about logistics.
At this point, I consider slides and visuals. This is the last step in my process because I go in assuming that there'll be an AV disaster and I won't have anything to use. Now, I may call on graphs or charts or things in my talk but I try heavily not to rely on them. People are here to see me present, and not my slides. I also tend not to have slides as a takeaway because they don't make sense out of context. (This doesn't satisfy anyone, so I want and need a better solution for this.)
I keep my slides simple, usually going for large photographs and supplementary text. If you think I'm one of those people who reads off of slides, you are wrong.
All of this takes place over as much time as possible obviously, but I plan to finish and be ready to give the presentation for real a full day in advance.
On the day of my presentation, I try to be in the space way ahead of time - maybe hours, if possible. This helps me feel comfortable in the room, making it my own. I always feel anxious and nervous just before the time I start - it happens. But once I start out I am quick to find my rhythm and go with it. I also know I'll make mistakes, but the audience may not know that.
And that's how I prepare.