I don't even think you should tell the audience you're improvising. It's like an apology in case it's bad : 'we're just making it up' If the improv isn't better than the rehearsed stuff, then you should just rehearse it.
Keith JohnstoneIf people had no fear, you'd hardly need to have to teach them. It's the fear that screws everything up.
Keith JohnstoneEvery time you go the way the audience expects, they'll think you're original. People laugh with pleasure at the obvious.
Keith JohnstoneGood impro can make you laugh, we love it, but soon the content is forgotten. Good scenes from The Life Game stay with you always. They haunt you.
Keith Johnstone