A user interface design pattern library for Drupal
“…Surgical teams that follow a basic checklist in the operating room, from discussing expected blood loss to confirming the patient's name, reduced the rate of deaths and complications by more than a third.” (source)
Drupal module development will hopefully not cost human lives one way or the other. But when building your module's UI the same principle is at work. It's all too easy to skip the basics, and go straight for the more complex parts of the problem. That’s the interesting part after all.