Drawing diagrams that effectively convey information about complex systems is both art and science. Open source projects and systems teams could more quickly, concisely and effectively communicate important ideas if they created some diagrams! Basic systems drawing is a fundamental skill that helps Based on 20 years of creating practical systems diagrams to reflect business process, software design and computer systems operations, this poster session will help anyone tasked with creating a diagram to do it better. The poster will demonstrate how to create effective diagrams with well-scaled icons, shapes, connectors and fonts; choosing the right level of detail; explanation of jargon that's used; a "blame" layer; logical flow on the page; single page per idea or system; and drill-down pages for more detail. Diagrams become invaluable with iterative refinement, an easily shared document format and a maintenance schedule. The poster will also include a list of common pitfalls in diagram creation to avoid, example diagrams and ideas to inspire viewers to create their own diagrams right away.