On the flip of this. For those getting started at their first speaking things, don't freak out when you look over the audience and feel like zero people are registering that you are even using real words :) . I've been on stage a lot: speaking, improv, plays, stuff. And there are countless times you'll actually be able to make some eye contact with the audiecnce if there aren't too bright of a stage light, and you will just see stone cold expressions staring back at you. And you will wonder if words are still coming out of your mouth. :) It happens. The human connection you get with a one on one encounter that your body kind of expects when you talk. Them nodding, or any expression whatsoever often goes completely absent in a speakers setting.

That's why "open with a joke" is so useful. It's not really for them! It's for you!. If you can hear a laugh from your audience, YOU start to chill out. Your body is like "ah. the mic is actually on, and I'm not having a stroke".

Another useful tip, if the scenario allows, try to hang out by the front row before your talk and chat someone up. That's who you want to then make eye contact with often during your talk. Their expression will be or at least seem to be warmer to you. And you'll feel some more calm looking at them than the random heads everywhere else.