At Norwescon, Mary Robinette Kowal gave many tips on how to read a manuscript in public. Her website gives many more tips, if you click on Fiction, then Reading Aloud. If you want something practical, this is it. Also, it has fun stuff on puppetry, which is her day job.
© 2010 Annaliese Moyer
Three of her tips apply to public speaking in general:
1) A good public reading speed is 150 words per minute. Pick a passage that has 150 words. Use a timepiece with a second hand to time yourself. You might be surprised at how fast you read. Practice this speed, and you’ll be able to maintain it in public.
2) Pick someone at the back of the room, and think that you are speaking to that person during the reading. It’s normal for a reader to speak to the people in the front rows, and the voice then comes out too quiet. Everyone needs to hear, so aim for the people in the back.
In a different context, the actor Michael Caine said that when he was doing live stage plays, the director told him there was someone sitting in the back of the auditorium who had paid to see the play, and he deserved to hear the dialog just as much as someone sitting in the front row.
3) Americans tend to speak from the middle of the mouth. If you speak from the back of the mouth, you can sound vaguely Russian: Open your throat as if yawning, then keep speaking from back there without putting on a Russian accent, and you’ll find the result surprising. (Although when I try it, I sound vaguely drunk, which may not contradict what she said.) If you speak from the front of your mouth, you will sound vaguely European (I suppose she meant Western European), without trying to put on a British accent.