Think about the first impression you create by the types of clothes you are wearing. If the organisation you are attending the interview for is very casual, then be sure that you are not overdressed for the first meeting. Very casual attire such as jeans is to be avoided in most instances and certainly at first interviews. If you are interviewing for a corporate environment, a suit (with tie for men) is the most appropriate attire. Clothes that fit your size, style and personality well will project the right message; that you are comfortable with yourself and care about your appearance. Looking your best is the key to creating a positive first impression and revealing how you care about your work and yourself.
So... dress for the job you want!