Although there has been a great deal of research on why individuals adopt and use information systems, there is little research on what it takes for individuals to use information systems effectively. Motivated by the view that much of the impacts of information systems stem from how they are used, we propose a model to explain the nature and drivers of effective system usage. The model is designed to explain effective system usage in the context of an individual user employing any individual information system. In this context, we build on a theory of information systems known as representation theory to propose that effective system usage requires a user to engage in three activities: adaptation activities (adapting the system so that it provides better representations), learning activities (learning how to access the representations offered by the system), and verification activities (verifying the representations in the system as well as the real world domain being represented). The model suggests a set of factors that drive these activities, specifies how these activities drive effective usage, and proposes a link between effective usage and users’ task performance. After specifying the model, we provide examples of how it could be used to explain the effective use of several types of information systems and we discuss how the model could be expanded to explain other contexts of use (e.g., multiple systems and multiple users) and to incorporate process forms of theorizing as well as variance forms of theorizing