Ask two improvisers to start a scene where the first handful of sentences are absolutely true. Not ‘we’re in an improv class’, but sharing views or memories. Give them a setting for the scene and they can do object work in the place if they wish.
Get the workshop audience to put their hands up when they see or hear something that feels unusual or out of place. They are beginning to identify possible ‘games’ that start organically. Offer one or more of these game ideas to the scene and get them to push into that idea.