Visibility Principle - Keep all needed options and materials for a given task visible without distracting the user with extraneous or redundant information. Feedback Principle - Keep users informed of actions or interpretations, changes of state or condition, and errors or exceptions using clear, concise, and unambiguous language familiar to users. Reuse Principle - Reduce the need for users to rethink and remember by reusing internal and external components and behaviors, maintaining consistency with purpose rather than merely arbitrary consistency. The system should speak the users' language, with words, phrases, and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.
Support undo and redo.
Make 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. Allow users to tailor frequent actions. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.