Tips for great UI design and web applications

Going along with the earlier post concerning tips for effective icon design, what tips you find helpful for guaranteeing a successful user interface design and navigation? Detailed task analysis can give UI and UX designers a more thorough understanding of the feature sets and their hirearchy of importance, but what rules assist you towards enhancing the user experience?

Some of the more established guiding principles include not forcing users to rely on their memory, providing multiple ways for users to reach their goals, keeping pop-ups to a minimum, making status messages easily noticeable, always providing users a quick way to exit any function, and not letting fear of scrolling dictate your design.