Designer Christian Siriano, 25, shot to fame when he won the fourth season of Project Runway in 2008. Since then he's been the reality show's most successful alumni, producing fashion lines for Puma, Payless, and, in addition to his own ready-to-wear collections—the latest of which showed at New York Fashion Week February 10. He's also partnered with Victoria's Secret and LG to design products and penned a memoir Fierce Style: How to Be Your Most Fabulous Self. Siriano took a break from the Fashion Week frenzy to share what he's learned about branding, buyers, and what to do when one of your models becomes fashion roadkill.

What's the most important lesson you've learned about building your brand? 

I learned very quickly that there could be so much hype and great press and I could have great girls wearing my clothes, but if the product isn't good, if it isn't selling at retailers, then you don't have much to go on. If every editor hates the collection but every buyer loves it and it sells, then there you go. You work for who's going to pay you. 

How do you stay true to your artistic vision as well?

Nikki Minaj, wore [one of my] gowns on Saturday Night Live, which was amazing and creative, and not every woman in the world can wear that gown, but it's great because I have that moment. And then I can sell a great little shift dress or a little wrap dress to a woman in Houston. It's the same with my collections. I'll show really wearable clothing but I like to close my shows with a big fantasy gown, because then it's still exciting for me. 

Are you still with Payless?

Yes, we've done [several] collections. We create these fantasy shoes for the runway and the shows—super sculptural and exciting—and then I get an opportunity to really play designer and really work for what real women can wear, everything from little flats to sandals, slingbacks, things for work, for day. So I get the best of both worlds.

Speaking of shoes, one of your models fell during your most recent runway show. How do you feel when something like that happens?

Our runway was painted, so it was very sticky and tacky and unfortunately, that poor girl, she just stepped and her foot didn't go forward. If every girl falls then yes, the shoe's the problem, but if not every girl falls, it's probably just that one girl. I also have my assistants wear the shoes backstage and they were running around all day and they didn't fall once! I was so sad, the poor girl was so upset she was really exhausted and I have to tell you these models, they go to like 25 castings in a day and they do like 6 to 8 shows. That's a lot for anyone to run around in the city. I mean, I can't get it done and I have a car service!