Imagine you work in a hardware store. You notice a customer puzzling over the vast array of electric drills.
She turns to you and says, I need a drill, but I don’t know which one to pick.
You ask “So, why do you want a drill?
“To make a hole.” she replies, somewhat exasperated. “Isn’t that obvious?”
“Sure,” you might say, “But why do you want to drill a hole? It might help us decide which drill you need!”
"Oh, okay," and she goes on to describe the need to thread cable from one room, to another.
A couple of days ago I found myself describing how to estimate the size of a story. It was coming out in my own words, without references. It felt... right.
One agile approach for "sizing" up a task is to use a relative scale to describe a mixture of effort, complexity and uncertainty.
So... first up, commit to heart the key statements of the Agile Manifesto.