Have good posture, with your weight fairly evenly on both feet. If you slouch, your audience will take you less seriously. If you have a lectern, rest your hands on it, but do not lean on it. Keep your hands out of your pockets.
As Xerxes said, speak slowly. People tend to speak faster when they’re nervous, and it shows. Slow down and relax. Don’t be afraid to pause for a moment to let a point sink in. There’s no rush.
For god’s sake, don’t memorize your speech. Reciting a memorized speech makes you sound stilted and ridiculous. You do need to know the subject matter, but not every word you’re going to say. However, if you do decide to memorize your speech, then practice it until your delivery sounds natural. then practice it some more.
Know your audience. What kind of presentation are they looking for? Do they want in-depth detail, or just an overview? Is it a formal speech or a casual talk?
Avoid use of slang or other inappropriate language.
I have to disagree with putting any distracting objects on the lectern. It’s a gimmick that keeps the audience’s attention, but you don’t want a gimmick keeping their attention. You should keep their attention. A gimmick will work only once, whereas good speaking skills and good speechwriting will work always be useful. (However, in this case, the gimmick would actually tie in to your speech…but I still think it’s a bad idea)
Use notecards if you are presenting more information than you can comfortably remember. Do not, under any circumstances, write out your entire speech and bring it on stage with you. Notecards should be an outline of the major topics of your speech, just enough to remind you where you wanted to head next. You shuld know the information well enough to merely need a reminder. (If I were giving this post as a speech, my notecards might say POSTURE, SPEAK SLOWLY, DON’T MEMORIZE, etc. The writing on note cards should be large enough that you can easily read it.
Use real examples and personal anecdotes to engage the audience. How does the information affect the audience? How does it affect you? A bit of narrative will change your speech from a dry presentation of facts to an interesting story.
Know how your speech is going to end before you start. If you have a list of points you want to make, great, but how are you going to finish? “Well, that’s my last point…I’m done” doesn’t work so well. You want something that brings all the information together to a central focus, and at the same time comes to a natural stopping point.
I hope these ideas are helpful to you. Sorry if I contradicted other folks, but I can’t resist adding to the general confusion.