If you have an interview on campus, there is no reason to dress sharp or prepaire. Usually it’s done by students. Just wear jeans and be yourself. Just requesting an interview shows interest. You don’t have to do anything spectacular during the interview. My daughter had an ingerview with a student when we visited last year. They sat on a bench outside and discussed which TV shows they both liked. It was very casual.
But definately find out who your rep is and see him/her as much as possible. If he comes to your school great, if not find out when he’s in the area and go there. More then once is good. At the end of the process my daughter was on the first name basis with the rep. He knew exactly who she was. And every time he saw her he remembered her name. When she got admitted, he personally called her guidance counselor to let him know. He was the one reading her app so in sure that helped.