Even if you're interviewing with Mark Zuckerberg, you shouldn't wear jeans and a T-shirt.
Granted, if you know the whole office is ultra-casual, you shouldn't show up in a suit. But you also shouldn't be quite as low-key as the rest of them.
"You go in the middle," Aimee said. "You're not as casual as everyone else is but you're also not too formal."
If you know everyone is in flip-flops, opt for baseline casual — dark denim and a nice blouse or shirt.