This guide outlines the process of organizing a hackday, which is a collaborative event aimed at engaging developers. It begins by explaining the reasons for hosting a hackday, such as generating enthusiasm among developers and serving as a follow-up to discussions or talks. The document details the essential components involved in running a successful hackday, including selecting a target, finding a suitable venue, and gathering assistance. It also provides examples of successful hackdays and emphasizes the importance of establishing clear goals, effective communication, and accommodating varying levels of experience among participants. Additionally, the guide suggests considering exercises to help focus the event, particularly for shorter sessions. Overall, the guide aims to encourage developer participation, facilitate learning, and ensure a productive and enjoyable experience for all attendees.