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 JohnstoneTrying to do better is trying to be better than you actually are, and I don't think you can do that.
Keith JohnstoneWhere if you're in a universe where you have to accept ideas, you'll never know if your partner wanted the garbage you're handing them. They have to take it.
Keith JohnstoneWhen you want to have entertainment, it must be a waste of time. I don't like that. I don't like improvisation being pointless.
Keith Johnstone