It's hard to stress too much the importance of preparation. When you are rehearsing your presentation, you want to prepare everything down to your mannerisms. If you've ever seen magicians/comedians Penn and Teller perform, you'll notice how much hand movement Penn uses. Perhaps originally a nervous habit, he's worked it in as part of his act. This is just one thing to consider when executing a presentation.
Where you stand is important, too. When using slides or visual aids, keep out of your audience's line of sight. You want eyes focused on the visual aid while you continue to talk. Don't read what's on your slides or screen -- explain what they mean. When you want the audience to focus on you, stand tall. Don't slouch. If you're in front of a podium, don't fold you arms and lean forward like you're watching a game on TV at a bar. Eye contact is fine in short bursts but not necessary.
When putting together your presentation, avoid using colors without purpose. The brain is wired to notice changes of colors, so adding some colorful words here and there is a good way to make something stick out [source: Wired Science]. But using them throughout the presentation will render them ineffective. Some colors can even trigger emotions -- red is often synonymous with danger, while blue may trigger feelings of safety.
As we said earlier, rambling can kill a presentation. And it's often spawned by nervousness or random questions. It's OK to ask your audience to reserve questions until after the presentation. If you feel nervous or begin to get hot, avoid apologizing when you feel like your anxiety is showing. Chances are your audience doesn't even notice. Have a glass of water nearby to sip when you need a second to collect yourself. Above all, stay on task.
Remember, your audience wants you to be successful. You're taking up your associates' and customers' valuable time, so no one wants to see you fail. Trust what you've prepared, and trust in your execution. Once you've seen that trust pay off, you'll become even more confident.