This goes without saying, but I still need to say it. At career fairs, representatives will be meeting you for 5 minutes at the most, so you need to make a great first impression. If you look your best, interviewers and representatives can focus on what you are saying and not the stain on the front of your shirt. Iron your outfit, brush your hair and pack a few breath mints, your interviewers will be happy to have met with you!