The wide scope of qualitative enquiry presents the researcher with a number of choices regarding data collection and sampling. Selecting data collection and sampling techniques can therefore be somewhat daunting, particularly because, often, there is no single, universally accepted ‘correct’ option. Appropriate research methods are, however, crucial to ensure high-quality research. This review, the second in the series, provides an overview of the principal techniques of data collection and sampling that may be used for qualitative research in nutrition and dietetics. In addition, it describes a process for choosing appropriate data collection and sampling methods that considers the extent to which they provide data that answers the research question(s) and are compatible with the philosophical assumptions about ontology, epistemology and methodology that underpin the overall design of a study. Finally, it discusses the central role that the researcher plays in qualitative data collection and encourages researchers to acknowledge and reflect upon their impact on the data. Other reviews in this series provide a model for embarking on a qualitative research project in nutrition and dietetics, an overview of the principal techniques of data analysis and quality assessment of this kind of research, and some practical advice relevant to nutrition and dietetics, along with glossaries of key terms.