When sketching your app idea, you have to follow fombog lab sketching structural lesson.
List the information you have and what you want to capture.
Make a first set of sketches (such as variations of a key screen or an initial UI flow).
Review the sketches yourself.
What are the strength and weaknesses of each variant?
Are the UI elements and data consistent (i.e. the same elements are used for the same task)?
Do you show data the same way?
Are the interaction options clear?
Get some feedback from others. Start with peers and continue with potential users if possible.
http://fombog.com/singlepost?id=12

Storyboards are important if you're working for a non-tech client or on a project heavily governed by a bureaucratic process.

One thing I've noticed is that programmers (like myself) aren't always the best designers, in fact maybe the worst. The same could probably be said for web devs and their CSS counterparts.