The field of human-computer interaction offers a huge portfolio of methods for interaction research—particularly for understanding the current situation and evaluating designs—and interaction design for envisioning and creating designs. However, there is little literature on the nature of the design situation and particularly its complexity, structure, and dynamics, as well as their influence on the choice of methods. This paper contributes a thorough analysis of methods for interaction research and interaction design as well as a systematic classification of those methods with respect to the complexity of the design situation and design circumstances. This will help researchers and designers get a better understanding of how to apply those methods for current and future research and design activities.