Usability Guidelines
Usability includes these five components:
- Efficiency - Make sure users can perform tasks quickly once they've learned your interface.
- Learnability - Make basic tasks easy to figure out for someone using your interface for the first time.
- Memorability - Users returning after a break should be able to get back up to speed easily.
- Errors - Keep user mistakes infrequent, limit their consequences and make them easy to recover from.
- Satisfaction - Make your interface pleasant to use.
Know your users. Define their goals. Define the tasks that accomplish those goals.
Watch someone from your intended audience try those tasks without guidance. Where they hesitate or fail tells you what to improve.