Suits
The best choice of fabric for a suit is pure wool or wool-blend in navy, black, or charcoal gray with or without pin-stripes. Single-breasted styles are considered a conservative look. Double-breasted styles are more trendy. Other styles such as muted plaids and tweeds in neutral colors are acceptable. The jacket sleeves should end at your wrist and the jacket skirt should cover your rear end. Button the top button of your jacket when you are standing.
Shirts
Wear traditional cotton or cotton-blend shirts with long sleeves and straight or button collars. White and light blue are recommended for interviews. Reserve pin-striped or chalk-striped shirts for less conservative situations. Shirts should be well-pressed and the collar should be loose enough to fit one finger between the neck and collar.
Ties
The best fabric for ties is silk, followed by polyester that looks like silk and silk-polyester blends. The tie should should end at the top of your belt line. For traditional professions choose from classic polka dot, paisley, or repetitive patterns in dark colors. In non-traditional fields or companies, such trendy patterns as florals may be acceptable. Avoid non-professional designs (no Mickey Mouse or Donald Duck ties!).
Belts, Shoes, and Socks
The best shoes for an interview are leather or simulated leather lace-up shoes, like wingtips. Choose dark colors like black, cordovan, or dark brown. Your shoes should match the color of your belt for a coordinated look. Dress socks should match the color of your slacks and go all the way over your calf (no skin showing please).
Jewelry
Watches and conservative rings are appropriate in any situation. Steer clear of items like bracelets and earrings, which convey a more casual look.
Grooming
Personal hygiene is essential in all professional settings, including clean and well-groomed hair; clean healthy nails; and well-groomed facial hair. A short, conservative hair style is the most professional. If you have a beard or mustache, groom it daily. In particular, your mustache should be well above your upper lip.