Where Should a Guide Handle the Unexpected?

A how-to guide can explain the usual path beautifully and still leave someone stuck when a permission is missing or an input looks different. Add every exception to the main instructions, though, and the guide can become harder to use than the task.

How do you decide what belongs in the main steps, what should sit in a troubleshooting note, and when the guide should direct someone to ask for help? What’s a useful way to check that choice with the people who will actually use it?