I have had to interview people in the past and there is no doubt in my mind that first impressions count. The first impression, before anyone speaks, is visual. Also, logical or not, prejudice cannot be avoided. I last had the task of conducting interviews about 30 years ago so things may be a bit different today - but human nature doesn't change and so I doubt it. I would expect someone seriously wanting to make a good impression to err toward the formal rather than the casual. Definitely wear a suit and tie. Make sure you have a clean shirt and clean shoes - not sandals. Don't worry about lapel width, pleats or not, and tie width - be more concerned with personal cleanliness paying attention to details such as finger nails. Make sure your hair has been recently had attention from your barber. As I've admitted, prejudice cannot be completely ruled out and I would find today's fashion for metal studs and face tattoos a real turn off. Just as important as dress try to look your interviewer(s) straight in the eye, smile and look confident. now accept the offered chair and let the interview proper start!