Or "How to Make your Project Manager Love You..."

When I was getting started in software development, our team always estimated in terms of days or weeks.  We'd have a task like "build the importer component" and we'd each say "oh, that's two weeks worth of work."

We hadn't fully defined what the "importer component" was. We didn't know how it fit together with the other tasks.  We didn't know what all the little pieces, tasks, and details that came together to make the task.  To be painfully blunt:

We were clueless.