A major part of a hiring decision is based on nonverbal elements in an interview - your handshake, eye contact, body language, posture, listening skills, clothing, grooming and accessories. Many hiring managers interpret your appearance in terms of what you know about the world around you and what attention you give to detail. The first impression you make on a potential employer is the most important one. The first judgment an interviewer makes is going to be based on how you look and what you are wearing. It's very difficult to overcome a poor first impression, regardless of your knowledge or expertise.

Before you go, be sure you really know the company you will be interviewing with, and research the industry that it's a part of to familiarize yourself with the universal dress code.