A powerful close leaves the audience with something of value to walk away with and relates directly to the opening. Restate a statistic or quote, or finish a story if that's how you began your presentation. When preparing a presentation, ask yourself what you want your audience to do and how you can convince them to do it. Even if you're trying to persuade people to use the information you're presenting, your delivery will be more powerful if there's a persuasive end in mind. Include objectives, benefits, and actions.
Most presentations are too long, too slick, and too convoluted.
Senior management doesn't have time to learn about your topic. Give them enough information to know how they can help. If you're giving a computer presentation, be prepared for problems. Have a backup plan for when your computer decides not to work, or when you can't get an Internet connection. Also, carry an emergency kit with an extension cord, spare projector bulbs, and backup copies of the presentation itself.