If you don’t know, I’ve got some opinions about Scrum, the Product Owner role, Backlogs, and User Stories. I’ve written a book about Product Ownership and I spend a great deal of my time up to my eyeballs in stories and backlogs at various clients.
One of the things that frustrates those clients is that there are very few “prescriptive rules or firm guidance” when it comes writing stories and crafting Product Backlogs; in many ways, it’s more art than science. It’s also a practiced skill that gets better the more you actually do it—of course as a team, which is also true of agile estimation.