I definitely found the big room effect scary at first even if I should probably have felt less pressure than presenting to my CEO in a small room.
And a random personal anecdote:
I had a really difficult time even at toastmasters dealing with my Uhms and Umms. Having someone count them somewhat works, but I decided to experiment by just watching my daily speech to be the same “quality” as public speech, and try to suppress the garbage words even during no-stress moments.
It took maybe half a year of practice, but as a result I started to speak slower and (probably :) clearer in the day to day life, and this during the public speaking too, with zero effort.
Edit-append: the most useful exercise is taking the projector, presenting in an empty room as if for the crowd, recording this “from a seat” and watching yourself. Extremely weird at first, but you very quickly see the areas to focus on. And since you must rehearse any talk anyway several times (at least that is the case for me), it is a zero-cost and high return activity.
There are two things at play with being too fast:
first, you know what you are talking about (thus are giving a talk) - and tend to want to give as much info as possible.
the second, and more important one, is the adrenaline rush that every performance gives.
It probably is this:
https://en.m.wikipedia.org/wiki/Tachypsychia
Consequently rehearsals help (they remove the worry about what to say)
Also one thing that helped me a lot is taking “dominant” poses five minutes before getting on stage. I can’t find the study that claimed it to work - but it did.
Later I have read the research that had claimed it didn’t work - https://www.ncbi.nlm.nih.gov/m/pubmed/28946020/ is one of the studies I could find quickly, but for me this technique still works, so maybe it’s the power of the placebo :)
The key seems to be repetition - just do it, realize it is OK, and do it again.
Good luck!
Maybe one day, I'll make a post to HN describing my first talk to a big crowd and how much I enjoyed it :)
Thanks all.