Many of you might have used SketchFlow for your various applications.
Now that there’s a Sketchflow template for Windows Phone applications, you can (and should) prototype any projects. The time you spend prototyping and working out any issues and finding ambiguities in requirements will be well worth it.
Here are some sample images from CodePlex:
Alternatively, see this video from Silverlight TV on how to use wireframes to improve the design and development process for Windows Phone applications