User-interface Design Principles

1. Define your audience -- user profiling
2. Use metaphors -- ideas and behaviors that are familiar to your users to help them understand new information.
3. Let the user see exactly what functions and features are available. No mystery meat.
4. Consistency; all aspects of the interface should be consistent -- eg navigational aids should not change appearance or position on page, or disappear/appear.
5. Highlight state changes -- changes in behavior or context should be communicated by visual changes.
6. Provide for different user styles -- concrete and abstract ways to get task done -- e.g search engine and site map.
7. Use focus -- visual hierarchy, colour, composition, movement and change to attract the users attention.
8. Understand the different kinds of help that a user might need and cater to them (e.g FAQ, searchable, step-by-step).
9. Provide a safety net -- e.g design in redundancy so that, for instance, there are multiple ways a user can locate where they are in the site/program/etc.
10. Provide contextual clues. Limit particular activities to single contexts.
11. Use aesthetics.
12. User test.