That said, there are two keys I train to address reflexive behaviors: counter-conditioning and external feedback.
Counter-conditioning:
Counter-conditioning is doing the complete opposite of the behavior in practice so that it is lessened in live execution. For example, to help people enunciate, I have them practice speaking with a pen in their mouth. Doing so requires so much effort that better enunciation feels like less effort once the pen is removed. Counter-conditioning verbal pauses is more difficult because they are so subconscious many people don’t even know they do it. Accordingly, one of the best strategies is to record yourself speaking and count the ums and uhs afterward. Doing so will prime yourself to be more aware of it when practicing the next time.
Reducing gestures through counter-conditioning is easier. To do so, practice talking at home with your hands pinned. Use a rope, a carabiner, belt, etc. – something that provides physical restraint. Every time you try to gesture, you’ll feel the physical resistance, and over time you will naturally reduce the level of gesticulation with which you are comfortable.
External feedback:
When addressing verbal pauses, I have the audience stand or sit every time the speaker says “um” or “uh.” As mentioned, verbal pauses are largely subconscious, so the distraction of seeing the listener pop up and down like a church service helps bring subconscious behavior into conscious thought. For gestures, it’s largely the same. Have trusted friends, family, or coworkers provide that external stimulus for you. Pick a phrase or signal they can use every time the gestures get too much, and try to make it as unobtrusive as possible while still grabbing your attention. The goal is to make you aware – not derail your train of thought (though this will happen a bit initially).
Rewiring your brain:
Reducing gestures and verbal pauses will feel borderline tortuous at first. Every time someone points out an um or hand flail, it will take you out of your flow, and it may take seconds or minutes to get back into it. Stick with it, because here’s the hidden key to understanding the above strategies: it’s not about reducing behaviors, it’s about learning to speak without them. Your brain needs to adjust how it forms and expresses thoughts without relying on the usual physical stimulus of gestures or the crutch of verbal pauses. Combining the above two strategies, keep going until you get to a point that nobody comments on either one anymore. Do it enough, and it will start to feel “right.” Just remember it will take some time and effort, and the first few times you lose your thought because of the disruption, that’s okay. Rewiring the brain is not a one-day event, but you can certainly get there.