Of course the usual scenario is the stuff of nightmares. It's when your boss, be it studio, network, client, director or producer needs something in a specific amount of time and has no idea of how to describe it. "I want the lead to look cool like Iron Man or James Bond. He's like Jaws mixed with Johnny Depp or George Clooney." And that's at least something. Most times it's just, "I want the lead to look cool" which can mean anything from Frank Sinatra to Lady Gaga.
It pays to have the presence of mind to ask questions but often you're trying to take in so much as to what is wanted that you don't follow up every point.
My Cartoon Network pilot has four leads. There's some important secondary characters and a major antagonist but if you can't crack the nut of the leads, you don't have a show. I found John Hoffman through Mira Crowell at Bento Box. Aside from being an artist herself, Mira works in production and also looks for talent on the internet. I liked John's stuff and so did the network.
As far as input, we told John which of his pieces were in the direction we liked. We talked other influences we'd like to see which turned out to be his influences too. Most importantly, he had the (overly long) pilot script. That's important because I don't want to tell him how to draw, I want to talk personality.
Both the network guys and I thought John hit one of the characters on the first try (and no, I can't show you anything) which is great for two reasons. The first, obviously, is that it's "one down, three to go." But more importantly, suddenly the universe of the series is partially defined. I told John to pin it to his drawing board because any character he came up with had to work with that one.
John does his thing and sometimes I'll play with his designs digitally. When I do, I make sure to show his original work as well as my own to the network. So we've got a bead on three of them but one character, the leader of the group no less, has been incredibly elusive.
The usual thing is to just keep drawing, trying different things like widening/narrowing/enlarging the eyes or changing outfits. I tried drawing poses that might suggest his personality but it was one of those "I can't draw" days. You look at the mountain of drawings and pick things that you like, "This coat, these eyes, hair like that, etc." You think you're zeroing in on the character but design breakthroughs rarely come from puzzle pieces.
You lose the element of being surprised. You think you're getting close but when you look at the sketch the next morning it looks like all the others. Best thing to do at that point is try something completely different. Save only what the story calls for and go in a new direction. At the very least it will give you a fresh perspective on the previous drawings. At best, you'll be surprised.
The design ceases to be a collection of shapes to be shifted around and becomes a personality. And that's what you're after.
So there's no magic method except trying to understand the character, the world it inhabits and draw until you find it. --Tad