Recruiters are really nice to all participants. No need to dress formal. Only group interviews, it consists of several participatory activities. In my case only a debate, but sometimes they do also a role play. They want you to speak up and participate! The best way to get noticed is to be active. They also show you how they work. You can sit beside a person who works already at air bnb, this person shows you how work will be. The whole process took approximately 3 hours.