The focus of interactive storytelling should not only be on the attributes of the technology or characteristics of the medium, such as the AI techniques, planning formalisms, story representations, etc. but also on the computer-mediated communication processes, such as the relatedness of transmitted messages with previous exchanges of information, the number of attributes to be manipulated by the player, or the level of player control on the messages. It is argued that an approach to maximize player enjoyment in a computer game is to customize/personalize the gaming experience and the associated computer-mediated communication processes. To this aim and to provide answers to “how” and “what” should be customized, the article first explores the problematic notions of interactivity and then frame the discussion in the context of interactive storytelling systems. Secondly, it analyses table-top role-playing games (RPGs) - the live counterpart of computerized interactive storytelling systems – in an attempt to find “what” to customize. In particular, it focuses on the Dungeon Master whose role in co-ordinating human-to-human communication process of interactive storytelling provides valuable insights into how to handle the human-to-machine/game communication process. Finally, the article proposes a framework to explain “how” to customize for maximum player enjoyment and optimal game experience within an interactive storytelling system.