[tobtoh]

I second this. I used to um and ahh very badly and I started debating in school partly to try and stop myself doing this. I had a teacher use one of the most amazingly effective techniques to help me - she filmed me once as I read my prepared debate 'speech' (filled with ums and ahhs), and then filmed me a second time, this time telling me to consciously be aware of the umming and pause before I did, gather my thoughts and then continue talking.

Watching the first video, I could see how distracting the ums and ahhs were. Watching the second video gave me a stunning insight. What felt like years standing silent as I struggled to suppress the um and continue my speech, actually came across as measured pauses. Not only did the pauses almost always appear 'normal', but they also made it easier to understand the points I was making.

In that one 15 minute session with my teacher, I became comfortable with pausing and that was the starting point for a dramatic decline in my umming.

[patio11]

This is about as close to a pure speech hack as I'm aware of, by the way. It makes you immediately, perceptibly better, and even if I told you "Here's a video of me talking. Hit a buzzer when I'm buffering" you'd miss most of them because they read as dramatic emphasis to the audience. (The umms, stammers, and verbal disfluencies, on the other hand, are instantly perceptible.)

As long as we're on the subject of hacks: pick three people in the audience: one on the left, one in the right, and one a bit off center in the middle. Always make eye contact with them when you are speaking. Rotate every couple of sentences. BAM, perceived confidence goes way up.