Progressive disclosure defers advanced or rarely used features to a secondary screen, making applications easier to learn and less error-prone.

The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.

Three Tips: Simplify, Simplify, Simplify.

Minimize the user's memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.

Throughout this book, we've been evangelizing simplicity, but ironically, the practice of simplicity is not simple. It is easy to build a bulky design by adding layer upon layer of navigation and features; it's much more difficult to create simple, graceful designs. Paring designs to essential elements while maintaining elegance and functionality requires courage and discipline.

Clear content, simple navigation and answers to customer questions have the biggest impact on business value. Advanced technology matters much less.

Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action.