There is no substitute for being prepared. Know your information inside out, backward and forward. The best way for you to look like you know what you're talking about is to actually know what you're talking about. Don't tread into unfamiliar territory. Cover only the information that you can knowledgeably and comfortably share with your audience. You need to project an air of confidence during your presentation, and this won't be possible unless you are at ease. Also, it's true that practice makes perfect. Rehearse your presentation until you can convey it without reading from notes (a definite "no"), manufacturing unnecessary pauses or using phrases like, "And uh . . .".
While you need to be an expert, realize that your audience doesn't want to know -- and doesn't have the attention span to absorb -- everything that you know about your presentation topic. It will require discipline on your part to narrow your focus, and then narrow it again, until you can select only a few of the most important (and interesting) points to share. For example, if you're doing an oral presentation on how technology can improve workplace efficiency, don't spend ten minutes discussing how the first computer was an abacus used in 300 B.C. by the Babylonians. According to Forbes.com, "speakers must make only their strongest points, and work hard to refine them down to their most concise and eloquent essence."
Slide show presentations and other visual props can be an effective way to add flair. However, used incorrectly, they can ruin an otherwise promising presentation. Spinning text is a nice effect; however, if it requires an additional 10 seconds for each bullet point to stop spinning, or if the text spins so rapidly that it makes the audience dizzy, use static text instead. Bells and whistles should complement your oral presentation. They shouldn't be the primary focus. "Presentation Tips for Public Speaking" offers this advice: "Do not over-dazzle your audience with excessive use of animation, sound clips, or gaudy colors which are inappropriate for your topic."
You've researched your information, you've whittled it down to a few relevant and interesting points, you've selected tasteful presentation props and you've practiced to the point of perfection. You're only halfway there. Now, you've got to be sure that nothing and no one can ruin your great oral presentation. Check and then double-check to ensure that neither the room number nor the time of your presentation has changed. If you're using visual aids, confirm that your room has a functioning projector screen. Verify that your microphone has batteries in it and works properly. Make sure that the presenter in the room adjacent to you won't be showing a video at the time of your presentation, which will drown out your audio and distract your audience. The Ohio Wesleyan University Library warns, "Do not expect a network connection to work when you need it. Have any web sites you hope to show available as offline copies; work offline whenever possible to avoid slow network response."