[drblast]

Best advice I can give: slow down.

Especially if you're nervous, a short time on stage can feel like an eternity so your immediate impulse is to talk quickly and fill every pause with speech. That's what's wrong with "uhhs," you tend to say "uhh" more than you normally would in conversation.

I had a professor who was a fantastic presenter and would pause frequently and for about 5-10 seconds to allow what he just said to "sink in." Then he'd smile and continue. Don't be afraid to do that. It's natural to pause and think about what you are going to say, even if you are giving a prepared speech.

[dmragone]

Learned a great trick from my old boss who gave a lot of powerpoint-based presentations. He would frequently add a "black" slide (as in nothing on the slide, completely blank, just one big block colored in as darkly as possible - a good alternative is to hit the "b" key on your keyboard) when he wanted to people to stop looking at the deck and focus on him.

It was amazing how everyone's eyes would go straight to him when that slide came up - they had nothing else to look at, and he could make a strong point, knowing everyone was paying attention for the next 15-30 seconds.

[michaelschade]

I made a conscious effort to do that more on a recent talk that I gave, and I felt so much better with the results.

It's surprising just how difficult it is to force yourself to pause for even a few seconds, but the payoff in terms of your audience having an opportunity to understand what you've said is completely worth it.

[tikhonj]

Yes! Speaking too quickly has probably been my largest problem. Even in normal conversation, I tend to speak faster than normal; when giving a presentation, it becomes even worse.

For me, slowing down not only makes the speech or presentation better, but also calms me down. When I concentrate on speaking slowly and clearly, I have less time to worry about other things.