Design for behaviour-change is a growing field with a great deal of potential. Changing the behaviour of users through products and services can help users be happier, companies be more profitable and also help mitigate environmental problems. My research goals were to gain a good understanding of human behaviour models, models of product-user interaction and design methods for generating concepts that solve behaviour-change problems. First, I developed an ontology to formally represent and connect the varied sources of literature. Next I developed a new way of studying and working with the notion of affordances and using that to design products that change behaviour. Finally, I discuss a multi-motive framework that allows designers to change the behaviour of users with different needs, apply many different types of behaviour change strategies and be able to work on problems of many different types. This model and design tool were tested with student and professional designers who both derived benefits from it. Directions for further development of this work include testing the efficacy of the products designed using the methods presented in this dissertation to change user behaviour.