Ask HN: Guides/Books on Representing Information Visually?

I'm trying to improve/supplement the state of my company's documentation. My team and customers seem to have trouble fully understanding process flows within the software, particularly when the flow is bi-directional. I've written lengthy write-ups before, but they seem to respond better to a 5-minute demo than 10 pages of documentation. I figured some visual diagrams might help. My company approved for me license to LucidChart (could just as easily be Vizio, the tool doesn't really matter), but I've noticed that outside of providing some templates, the LC resources don't give much by way of general information theory. I'm assuming that someone smarter than me has thought about this already and come up with some best practices (e.g. 'When illustrating a one-time process flow, use this; when illustrating a repetitive, circular, or bi-directional flow, use this', 'Labels along connecting pipes between steps should represent processes, not objects', etc). I'm curious if HN can recommend any resources for learning how to represent information on a diagram, as opposed to how to use a specific diagram tool.