We work with end users to test our initial ideas. We encourage them to look at the sketches, without input from us. Our goal is to get their initial reactions. We quickly learn what is intuitive, what assumptions are correct, and which are wrong. We encourage the user to describe what they believe they have in front of them. Often the big ideas are validated and we discover the small issues which have distracted the user.
From the user feedback sessions, our design team distills down the set of good ideas to focus on what could be the great idea.