1. Place users in control

Use modes judiciously (modeless)

Allow users to use either keyboard or mouse (flexible)

Allow users to change focus (interruptible)

Display descriptive messages and text (helpful)

Provide immediate and reversible actions, and feedback (forgive)

Provide meaningful paths and exits (navigable)

Accommodate users with different skill levels (accessible)

Make the user interface transparent (facilitative)

Allow users to customize the interface (preferences)

Allow users to directly manipulate interface objects (interactive)

2. Reduce users' memory load

relieve short term memory (remember)

rely on recognition, not recall (recognition)

provide visual clues (inform)

provide defaults, undo, and redo (forgiving)

provide interface shortcuts (frequency)

promote an object-action syntax (intuitive)

use real-world metaphors (transfer)

use progressive disclosure (context)

promote visual clarity (organize)

3. Make the interface consistent

sustain the context of users' tasks (continuity)

maintain consistency within and across products (experience)

keep interaction results the same (expectations)

provide aesthetic appeal and integrity (attitude)

encourage exploration (predictability)

Source: The Elements of User Interface Design, by Theo Mandel, Wiley Publ, 1997.