If you're a woman, wear an outfit that is neatly pressed with a matching handbag and unscuffed shoes. Pump up a monochrome suit with a colorful scarf or with funky jewelry. If you really want to make a statement, wear a bold color like lime or orange. Even if that color is only in your briefcase and shoes, it gives your audience the impression of confidence.
For males, go with a navy suit because this is the color that wreaks confidence. Pump up your image through a thicker-striped dress shirt and a bold tie. Be detail oriented in your choice of briefcase and writing instrument, as they can also be used to make a strong impression. Don't forget to buff your wingtips as well! If you carry through that initial impression with a strong message, an upbeat delivery and a firm handshake, you'll be on your way.
Best of luck!