Student engagement in science, technology, engineering, and math (STEM) through informal outreach events is critical to the current educational pipeline. National Biomechanics Day (NBD) is a STEM outreach event that is an international celebration of the science of biomechanics with the goal of introducing high school students to the field. While NBD has experienced global success and substantial growth in recent years, it is an equally rewarding and challenging endeavor to host an NBD event. In this paper, we provide recommendations and mechanisms for biomechanics professionals to support their success in hosting biomechanics outreach events. Although these guidelines are framed around hosting an NBD event, the underlying principles can apply to hosting any STEM outreach event.