To pick up tips about timing, humour injection, giving just the right amount of information for folk to understand without getting lost etc, it's worth watching a few of former President Obama's speeches. Some of them were about as close to perfection as it's possible to get.
I'm not sure how you'd do this by yourself, but it was an incredibly quick way of fixing it.
Get rid of the annoying habits. Unfortunately, you need to be brutal with this. On my course, on the second morning once everyone had built into a team and it had started to become a bit of fun - they put the presenter at one end of the room and everyone else at the other. They started speaking and we were encouraged to shout out faults! "Too quiet", "EEERMMM", "Too fast", "Too fast", "Too fast", "Too fast", "Pause NOW", "Pause NOW", "Get your hand off your face!". I'm not sure how you'd do this by yourself, but it was an incredibly quick way of fixing it.
I think the most important point when public speaking is to remember that you are in charge of the rate of speaking. The worst thing you can do is to gabble.
If you are using a Powerpoint presentation, don't just parrot the lines. The presentation needs to be a framework on which you can hang a discussion.
.... Make sure you have a glass of water to hand so you can use it as an excuse for a pause if you need one. Better still, get a jug and create a few seconds of extra space by filling your glass before you drink from it.
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