The use of ambulatory assessment (AA) and related methods (experience sampling, ecological momentary assessment) has greatly increased within the field of adolescent psychology. In this guide, we describe important practices for conducting AA studies in adolescent samples. To better understand how researchers have been implementing AA study designs, we present a review of 23 AA studies that were conducted in adolescent samples from 2017. Results suggest that there is heterogeneity in how AA studies in youth are conducted and reported. Based on these insights, we provide recommendations with regard to participant recruitment, sampling scheme, item selection, power analysis, and software choice. Further, we provide a checklist for reporting on AA studies in adolescent samples that can be used as a guideline for future studies.