If playing with only actors no audience participation is required. If playing with the audience, they will need to suggest motivations for the actors.
Two actors begin a scene. Once the scene is established, the host pauses the action and asks either the audience or other actors not included in the scene for a motivation for each of the actors. For example, one actor's motivation might be to reveal that they have a crush while another might be looking to make their fortune. Once each of the actors has a new motivation, they continue the scene as best they can. At any time, the host may pause the action to get a new motivation for each of the actors.