User interface design can be one of the more challenging aspects of building an application. To build interfaces your users can navigate with ease, you need to understand the users’ expectations and goals. It’s hard to put yourself in their shoes and think about what they want, but if you have a partially working application in front of you, it can be a lot easier. What is already there inspires you, and what is missing grabs your attention.
Just as a picture is worth a thousand words, a working prototype is worth a thousand meetings.