This chapter presents a systematic analysis of research methodologies for investigating teacher design thinking and practice, drawing from our multi-year research program. While design thinking remains an unobservable cognitive process and teaching practice occurs in complex, dynamic environments, researchers can employ various complementary methods to understand how teachers approach and implement their design work. We examine the evolution of our methodological approach through four distinct case implementations: from initial single-method retrospective interviews to comprehensive longitudinal studies combining multiple data collection techniques. The chapter details both introspective methods (think-aloud protocols, interviews, and design diaries) and observational approaches (simulated and naturalistic design tasks), analysing their respective strengths and limitations. Through detailed case studies, we demonstrate how different combinations of these methods can capture various aspects of teacher design work, from initial planning through classroom implementation. We consider the practical challenges and opportunities each approach presents, including data collection strategies, analytical frameworks, and implementation considerations. This systematic examination aims to help researchers select and combine appropriate methods for their own investigations of teacher design practices, while highlighting the importance of methodological triangulation in understanding this complex phenomenon.