Pam Slim provides a great list of things to do prior to making a presentation. If you make speeches, presentations, or pitches, you need to read this.
Here’s one more power tip: Show up with your own Countryman E6i microphone. (And tell your host that you need a Shure or Sennheiser body pack.) This has two effects. First, you will be using a great microphone.
Second, you will impress the audio-visual dudes backstage. These folks can make your presentation go a lot smoother—or tank it—so you want them on your side. And few things will impress them more than a speaker who carries his own E6i.