Your introduction is extremely important, but don’t begin with it. Let’s face it, intros are boring. The best way to start is with an attention-getting device (AGD): a joke, anecdote, quotation, etc. Once you have your audience’s attention, give the introduction. This should state, in the most interesting way possible: who you are, the reason why you are giving this speech, and a reason for your audience to keep listening. Immediately following should be a brief summary of your speech’s content. Whether you are persuading someone to buy your product or simply telling someone that Picasso wasn’t insane, your audience needs to know what’s coming.
Examples must support your initial point. A good number is 3-5 examples, giving you enough material to cover your point adequately without boring your audience to death. A small amount of humor helps to keep your audience listening, but if you try to keep them laughing, they will not only be disappointed when you switch to being serious and so be unlikely to listen, they will also be unable to take you seriously. Dry humor is better than flat-out comedy. Your examples should establish you as an expert in whatever field you are talking about; for example, if I was selling something to speed up computers, my examples would all be about bandwidth, pipe size, etc.
Your conclusion should be confident. This is where most speeches trip up: if you are unsure of your conclusion, your audience will see it and be unsure if your entire speech was genuine. The conclusion should summarize again your examples and restate your identity. In addition, if you are selling to a large corporation, hand out business cards with full contact information. Again, confidence is essential to ending your speech well. The last line of your speech should be powerful and (if possible) slightly philosophical. When you are done speaking, thank the audience. You may not be able to change the world with a great speech, but you can try.