The self-organization of communication conventions in a population of agents is object of growing attention. Besides its intrinsic theoretical relevance, in fact, it has recently acquired importance for many applications to artificial and distributed systems. In this talk I will illustrate a very simple model in which agents play pairwise games in order to negotiate conventions, i.e. associations between forms and meanings. The model describes the emergence of a communication system and in addition exhibits a rich phenomenology, while its simplicity makes it suitable for analytical approaches.