How can an audience become involved in a theatrical performance?

From my experience, some good ways to involve your audience in a theatrical performance, is to have them talk back. Ask them a question, and then they can all shout an obvious universal answer. For example, the performers may say "When I say , you say Yay! --" then they can respond. Or, you can say, non directly, but to make it seem like your speaking and interacting, you can say "hey, kids!" or, "parents, are we having fun, tonight?" or things like that. I hope that I helped :)