In this chapter, the reader is introduced to various methods of data collection: surveys and questionnaires; observational methods; experiments; systematic reviews and meta-analyses; qualitative methods. We highlight the pros and cons of each of these approaches to help the reader to better evaluate studies that have employed any of these techniques. In addition, we consider randomized controlled trial methodology and different types of bias within them; reporting guidelines that can be used to more clearly present the methods and results of experiments (Consort, Trend, TIDieR); and different types of intervention synthesis (single trial-based choice; common components hybrid; model guided synthesis) that can be used to translate the results of systematic reviews into practical treatments.