When I first wrote OSRIC, I couldn't put my finger on why I felt it was so important. I've got another interesting example of that, on a smaller scale, and I'd love to hear some input.
I'm working with a teenager who's writing their first module for general consumption. The very first thing I did -- and I don't know why -- was to have them open a commercial module and read it for 5 minutes, telling me what they were looking at as they went.
The result was a lesson that most of us know. No one reads a module sequentially. You flip around from introduction, to maps, to interesting locations you see on the map, etc.
What I don't know is why I felt so intently that this was a FIRST lesson in writing a module.