I can talk about something completely different– I'm a writer, and I work with visual designers. They much, much prefer it when I can give them a terrible sketch of an idea rather than a lengthy diatribe about what I want. Because it's far easier for them to apply their design sensibilities to a crappy sketch than to a cloud of words.

Similarly- I don't think it's "show me a cool semi-working website and I'm on-board", but more of- "Show me something that I recognize immediately as a really good idea, even though it's kind of crappy in execution."

I'm reminded of what Jong-Moon Kim wrote about Pixar movies: http://jiggity.com/kitchen.html

> Pixar uses a structure known as a braintrust to delicately examine works-in-progress. The braintrust is composed of some of the best storytellers of our generation who take a supreme effort in understanding the director's intent before offering suggestions.

> What's most incredible is that this feedback from the world-class cabal is merely suggestive and the director has the power to reject changes. The braintrust is aware of the danger of heavy-handed feedback squashing the soul of the product.

> New ideas are delicate and brittle. What starts off as a ugly, tangential feature later grows up to become a fundamental part of the final product.

That way you can demonstrate that you at least know what you want a finished product to roughly look like and do.