How do you speak on a subject when you are not an expert?

1 I wrote a book on etiquette and when I spoke on radio on etiquette I was asked why Americans eat with a fork in their left hand. I didn't know - but an American rang in with her answer. I learned that if you can't answer a question, you ask the audience. If none of them know, it doesn't matter that you don't and you can say you'll find out and let them know later. If somebody does know, you can thank them profusely.
2 You look the subject up in Wikipedia. In advance. You find the world expert on the subject who has written a book. You pick a pithy a quotation on the subject. You ask who in the audience has read the book and what they thought of it.
3 If you are asked suddenly (the speaker didn't turn up) try to get a break at half time during which you check wikipedia on your laptop or mobile phone for more ideas.
4 You ask the audience for their biggest problems and then ask who has solved that problem. You'll soon find you have a relevant or amusing or helpful comment on their methods or attitudes.
5 Turn it into a workshop. Start by flattering the audience for being such a group of experts. Ask the list of their top ten challengers and get a VIP to write these on a board. Break them up into groups of 2 or maximum ten and give them 20 minutes and then get them to give feedback. (While they are doing this, you can research the subject on the internet.)