With an increasing focus on preventing the amount of food discarded by consumers, there is a need to understand not only what and how much food is wasted, but why it is wasted. Qualitative research is critical to understanding the food waste phenomenon and makes an important contribution toward designing evidence-based interventions. This chapter provides a brief overview of research on the causes of consumer-level food waste. After a brief explanation of dominant theories on consumer behaviour, theories of practice is further explored. As an alternative to traditionally individual approaches to behaviour, theories of practice provides a robust analytical framework for understanding how social, cultural, material, and other contexts influence how food becomes waste. The remainder of the chapter focuses on two methods, ethnography and diaries, which are well aligned with a practice-based approach. A detailed overview of each of these methods is given, including benefits and limitations. Overall, this chapter provides an analytical toolkit for academics and practitioners to use when researching food waste at the consumer level.