When rehearsing record yourself (i.e. with your phone mounted on the tripod or just against something). I realized, that before that I didn't do full rehearsal, just was repeating the talk in my mind or even if speaking aloud - I was sitting instead of standing, had lots of interruptions, etc.
Then watch the recording. It's painful, but worth it.
Observe your body language. Try to face the audience, not sit or stand with your back towards them to read the slides. Move a little bit, don't just stand there.
This. When rehearsing in your head, it's easy to gloss over parts that really need some working. When treating it as a proper presentation, those spots are painfully obvious. Better to find them alone, even if watching yourself is a bit awkward.
I also like to record myself because sometimes I find a good way to explain something, which I want to remember and explain the same way during my talk. It also helps with pacing. Am I too slow or too fast?
