People make first impressions not only by what you say, but by what you wear. It is often said that interviewers gauge their candidates very early and hence dressing up will help in your cause. Make sure you look exceptionally nice. Pressed pants, (not jeans!) and a nice shirt will make your interviewer realize that you take this seriously.  Loud and obnoxious hair colors are not considered "professional". Unless you already know the person interviewing you, don't get judged by your hair dye choices. While all your friends may adore your bright blue hair streak, it's not appreciated in most work areas. Pop a wig on, if needs must. Dressing aptly reflect that you are interested in taking up the job.

Summary:
Dress appropriately.