Developing a software system by first creating a large number of detailed diagrams is an approach that, in our experience, does not compare favourably to the alternatives. However, describing a particularly complex and intricate part of the system with a diagram is usually a good idea, and the UML itself offers a number of useful and commonly understood diagrams. We like PlantUML for creating these diagrams because it allows expressing the intent behind the diagrams in a clear textual form, without having to fiddle with overloaded graphical tools. Having a textual form also allows versioning and storage alongside the source code.