If you want a codified set of rules that you can mechanically apply, I would look at UML and C4. However, I'd argue that the frameworks are overkill for the vast majority of engineering diagram use cases.

For the general scenario where you're just trying to communicate a technical concept clearly without spinning your wheels a lot, here are a few tactical things I'd recommend:

1. Pick the right diagram type for the job. Sequence diagrams are great for API documentation, ERDs are great for database schemas, flow charts are great for user flows, data flows and logical flows.

2. Use icons where possible. A database icon, a S3 bucket icon, a cylinder shape are all a lot more expressive and easier to grok than a rectangle with text inside that says "database".

3. Focus on the nodes, groupings, and connections. That's really all there is to a diagram if you break it down. If you just make a list of nodes, groups, and connections that you want to represent, the diagram will almost just draw itself.

4. If you're looking for a quick way to start jump start a diagram or looking for inspiration, try AI tools to see how far they can get you.