Never criticise the audience.
Once I saw a presenter ask, “Who knows what coaching is?” A boy of around 17 raised his hand and gave his view: the presenter jumped in with, “No, no, no, that’s a big mistake! Let me tell you what coaching really is...”
The young lad shrivelled into his seat, humiliated. Even if an audience member says something that is off-track or plain wrong, tell them, “That’s a way of looking at it.” Then add your own steering of the subject back towards where you want your message to go.
Keep questions to a very few.
It can be gruelling to be up-front and handling questions. I would recommend five or six at most, and when you’ve reached five, make it clear you’re about to end: “I’ll take this question and one more, then we’ll wrap it up.”
If they clearly still have more to ask, advise them to send by email or to approach you afterwards. Being accessible is important: it makes clear that you genuinely want the audience to take action on your message.