I was a manager at A&F for 2 years. The thing that annoyed me most was when people would come to the group interview wearing a competitor's brand. Also, when people brought a friend with them or their MOM!
Just be outgoing and look natural (not a ton of makeup or crazy hair). The interview is super quick and the questions are easy. Some example questions are: How would others describe your personality? How would you describe the brand? What's the definition of diversity, and do you think it's important in the workplace? What makes you a good hire for the company?