One piece of advice I've given (especially to students and young professionals) is to slow down your rate of speech. This is important for a number of key reasons:
1. We tend to speak more quickly when we're nervous and our audience can pick up on our anxiousness.
2. Slowing down your rate of speech can have a calming effect causing a virtuous cycle that will reduce your nerves.
3. The human brain can only digest a limited number of spoken words per minute. If you're pushing your audience's limit you're making it more difficult to get your message across. Remember: When you're speaking live to your audience they can't hit the rewind button. An audience that's not keeping up with you is an audience that is tuning out.
4. When you're not rushing you appear more confident. Cool, calm, and collected. My personal preference is a slightly slower than average pace. When I think of pacing I think of Presidential speeches in particular.
5. Slowing down your rate of speech is especially important if you are looking to establish credibility. A quick speaking pace is generally associated with youth. (Fair or not, I think of teenagers.) A young professional who slows down a fast-paced speaking style can instantly sound more authoritative.