At an airport cafe, two young, White men wait for their food. The server arrives carrying a salad plate in one hand and a meat pie in the other. The meat pie eater waves his fork in the direction of the salad, and sneers "Got the healthy option?" Sarah, overhearing their conversation thinks, "Well, that man' s never ordering a salad again." In that moment, there is a lot for a psychologist to study, including what they said next, how they interpreted the conversation, or the wider discourses underpinning this "food talk." Deciding what to study and how to study it means thinking deeply about research, and, in this chapter, we provide some foundations for this thinking, starting with the big question: What can we know, and how can we know it?