Part of MUN conferences include dressing professionally which helps to establish a clean, polished look and shows that you are ready for the conference!
Here are some guidelines that will have you looking distinguished and stylish on the day of a conference:

Boys:
 - Suit: wear a well-fitted, dark-colored suit (usually black, navy, or gray)
 - Shirt: a light-colored dress shirt
 - Tie: preferably in a solid color or not too flashy pattern
 - Shoes: polished dress shoes (black or brown) 

​Girls:
 - Suit: either a pantsuit or skirt suit in a dark color (or a dress with a blazer)
 - Blouse: a light-colored blouse or shirt
 - Skirt/Pants: skirts should be close to knee length or longer
 - Shoes: preferably low to mid-heel (some conferences might have a bit of walking)
 - Accessories: minimal jewelry (keep it professional)