1. Begin with "Hi, my name is" The sentences most likely to be remembered by the audience are the very first and the very last sentences you utter. Don't throw away the opportunity to do something meaningful in the opening line.
2. Make a false start. Avoid apologies and tentative statements that can put your credibility in question. Some typical phrases to avoid are: "Well, here goes," "Where shall I start?" and "Can you hear me OK in the back?"
3. Use a rhetorical question. Typically they result in an awkward moment. Because the audience is unsure if a response is really desired by the speaker. This can erode your confidence.
4. Go overboard. You want to be creative and innovative in attracting audience attention, but your opening should be consistent with your personality and with the tone of the rest of the speech.
5. Fail to consider how you'll get to the podium. Speaking areas are often crowded and nothing destroys your credibility like tripping on the way to the front of your audience. This happens to someone famous every year!