While much of the attention- and pressure - surrounding fashion week is focused on the designers and their clothes, the week can be just as defining a moment for models. And few assignments signal a model's success like walking the runways at New York's fashion week. But it's a long, competitive process the leads up to the first stiletto hitting the catwalk.

Douglas Perrett is a casting director and in charge of securing models for six New York fashion week shows this year, including Vena Cava, Benjamin Cho and Verrier. He sees more than 300 girls the week before the shows; he casts about 100 of them. Mr. Perrett, 27, also runs the "Confessions of Casting Director" blog, where he catalogues new faces as well as Vogue cover girls like Chanel Iman and Jaslene Gonzalez, winner of "America's Next Top Model."

The Wall Street Journal Online's Elva Ramirez followed Mr. Perrett through the casting process, as he winnowed down the field one walk at a time, all the while seeking this season's new "It" girl.