We are now living in smart cities, where information technologies enhance our everyday life. For example, our energy management and traffic management have become smarter, making our daily lives more convenient and efficient. However, from a citizen's point of view, a person's happiness needs to be more important than achieving efficient and convenient smart city infrastructures. This is, in particular, an essential issue for achieving humancentered smart city design. In this paper, we present our methodology to gamify smart city services. Our methodology consists of three tools, one model and two infrastructures. The tools contain the value-based design framework, the personality-based analysis framework, and the reality-based analysis framework. The model is named the GamiMedia model, and the infrastructures include the Virtual Form infrastructure and the Digital-Physical Hybrid Role- Playing infrastructure. The methodology to gamify smart city services is extracted from our long experiences with building applications services and middleware infrastructures for ubiquitous computing environments.