In this first part of the article, we aim to provide health researchers with an understanding of how to design a qualitative health research study, including: topic identification, design selection, and engagement in reflexivity. We offer practical guidance for writing an overarching question using a novel framework that helps develop a clearly articulated question that includes the following elements: emphasis, purposeful sampling, phenomenon of interest, and context. We then expand on specific methodological issues: study designs, contexts, sampling, and recruitment. Finally, we provide examples of qualitative health research studies that illustrate the application of different research designs. In part two of this article, we will discuss how to prepare for going into the field, how to generate, manage and analyse data, and plan for the dissemination of qualitative health research.