NOTE: Your eye color is important to know in order to narrow this list down.
GENERALLY, if you have dark hair but are very fair in tone:
SHIRTS: Avoid white shirts (unless you're wearing one underneath a green/burgundy/red sweater. Dark blue, light blue, light green, grey/charcoal dress shirts are great. Pin-striped shirts with these colors (or a burgundy) would work well. If you're in t-shirt mode, anything but beige -- or those really thin white cotton tees.
A fun T-shirt logo can be a good ice-breaker, but avoid anything vulgar.
SWEATERS: Black, Grey/Charcoal, Navy, Forest Green, Burgundy sweaters/hoodies would generally work well with the shirts described. Primary colors usually work well with the dark hair HOWEVER (again), depending on your eye color, some colors will make your eyes "pop" and others won't.
PANTS: Darker jeans or dark "stone washed" are best -- boot cut will emphasize your build without making your legs look "thin". Black/grey slacks.
MATCHING: If you choose a print shirt, don't wear a print tie with it. It's tacky. Wear a solid tie and sweater. If you choose a solid color shirt, you can wear a print tie OR a print sweater (not both).