Chris Anderson is the curator of TED and has written an article with some excellent suggestion on how to give a presentation of TED-like quality. Some of the points discussed in the article:

• Plan your story: beginning, middle, end
• No jargon, keep things conversational, cut back on the ego, show that you are vulnerable
• People do not relate to descriptions of organisations/institutions
• Do not try to cover too much ground, you need to go into some level of detail to keep things interesting
• Let the audience draw conclusions themselves, not everything has to be spoon-fed
• Really, really, memorize your talk in order to be spontaneous. Sort-of memorising is the worst, you are not your improvising self, but the words do not flow either with frequent memory pauses giving away that you are playing off a script
• When rehearsing, think what feedback you need to take in, and what not. Usually, experienced speakers give the most useful feedback
• Stay relatively stationary on stage, emphasise with arm gestures, keep eye contact with a few people in the audience
• Use slides only if you have to make a point that needs visual backup
• When using video: keep it short, and think twice before including a sound track
• Final advice: be yourself