The biggest mistake I ever made during an interview is showing arrogance. Later I learned the interview panel never entertain this sought of behavior and for the whole interview, it felt like I’m sitting on a chair made on iron nails. I learned it the hard way and I strongly suggest you learn right now. Not a good experience to have.
Swag and attitude are just words on the street instead, be professional and polite once you step in the interview room. Be confident but not over-confident.
