My research desk. The cats are strangely NOT in the picture.
A good story on an interpretive sign is similar to an iceburg. When done well, there's a mountain of research in front of, underneath, behind, and beyond what's visible in the short story told on the sign. The tasks are:
Suss out the foundational stories.
Comprehend the overarching concepts.
Gather relevant facts - mindful of the main story.
Check the facts. Facts ARE real.
Find the good, bad and the naughty bits.
Remember what story the CLIENT asked for.
Remain open for unexpected stories that will pop up.
Sort through all the research for the most interesting and relevant parts.
Be a multi-task wizard.
Once the research has been gathered and ingested, it's back to the original purpose, to tell the story in simple and easily accessible - but not dumbed down - language in 3 paragraphs or less. Oh, and in a very structured hierarchy of concepts and format.
I've acquired a love of, and as my kids would say, "mad skills' for digging up stories. Let me dig up yours. I'll write your story too.