The author recently delivered an online professional development session on running STEM clubs as part of a Primary Science Quality Mark (PSQM, www.psqm.org.uk) Teaching and Learning Festival. It is a topic the author is often asked about, and she frequently provides training and advises teachers and external organisations on the what, why, how, where and when of STEM clubs. This article aims to share that advice so the reader can get as much from their club as possible. If the reader is already running one, then this article may help make it even better!