Simple is classic. Attention should be on you and your words, not your dress, pierced body parts or hairstyle. Some colleges have scholarship weekends and require that students dress in a semi-formal attire for the formal interview. These interviews are often before a panel of 3-4 professors. Practice your entry.
Eye contact is important.
Walk into the room with shoulders back and head held high. Look at the panel or representative and smile. If others offer their hand for a handshake, accept. Handshakes expose a part of your personality. A weak handshake indicates a non-assertive personality or someone who lacks confidence.