To improve the quality of programs we provide an approach to guidance in the process of program development. At the higher level the various activities and their dependencies to structure the process are identified. At the lower level, detailed, practical rules are given for the decision-making in the development steps during these activities. The approach concentrates on structure and behavior of a single class. It includes design and specification and is compatible with methodologies for programming in the large. Informal specifications are introduced to help develop correct and robust code as well as corresponding tests. A strict distinction is made between external design and specification on one hand and internal design and specification on the other hand, which helps in keeping control over complexity. The approach also exploits the separation of success and failure scenarios. A worked-out example is provided.