Abstract Dietary intake and food habits are important contributors to the obesity epidemic. They are highly modifiable components of energy balance and are usually targeted in both obesity prevention and treatment programs. However, measurement of total diet creates challenges and can convey a large burden in terms of cost, technical expertise, impact on respondents and time. It is not surprising therefore that comprehensive reports of dietary intake in children are uncommon and, when reported, have limitations. The aim of this paper is to guide researchers and practitioners in selecting the most appropriate dietary assessment method for situations involving children and adolescents. This paper presents a summary of the issues to consider when choosing a method, a description of some of the more commonly used dietary assessment methods for young people and a series of case-studies to illustrate the range of circumstances faced when measuring dietary intake. We recommend that researchers consider the specific components of dietary intake addressed in their research and practice, and whether diet should be reported comprehensively or as targeted components. Other considerations include age, cognitive ability, weight status, physical activity level, respondent burden, and reliability and validity in the context of program goals and research questions. A checklist for selecting the appropriate dietary methodology is provided. This guide aims to facilitate the reporting of dietary intake and food habits in the context of obesity using valid and reliable measures, thus contributing to the evidence-base for nutrition policies and programs relating to obesity.