How do I know what messages and topics will be interesting to my audience? Well, here's a radical suggestion. Ask them. You're speaking to 50. colleagues at industry trade association event, two weeks from Tuesday, call or email three or four of them. Tell them that you're speaking you're looking for ideas, and give them four or five ideas. Ask them to rate them in importance, email it, call them up and ask them.
You don't have to guess you don't have to wonder, because you might guess wrong. There's certain things of interest to me that nobody else cares about. I'm going to waste my time if I just guess and talk about what's interesting to me. So my recommendation, ask that now sometimes you have to make a guess based on your gut. But these days, it's pretty easy to email someone call make a post in a forum. post something on Quora.
A lot of different ways of getting feedback in advance. You can test in advance you don't have to do all the testing on your live audience.