Of course you have to know what to improve. If you don't know, ask around - not for vague reassurances, but for specific points that could be better.
Speaking too softly? Speaking too fast? Not enough enthusiasm? Not enough animation? Not enough eye contact?
I'm not talking about probing questions, I'm talking about loaded questions and interjections. Emotionally loaded.
Here's an example. Imagine this (with an angry tone) "I don't believe this! You made us do this last year and it was a disaster!" (Several nods around the audience.)