Article: Always tuck the shirt in and pair the shirt with an appropriate belt. For business casual, tie is optional.  White button-down shirts are the most formal and therefore the safest. Unlike pants, all manner of shirt colors are acceptable: Purple, pink, yellow, blue, and red. Choose shirts (and pants) in "formal" fabric: Cotton is king, and comes in many different flavors. Wool is acceptable, if itchy. Silk, rayon, and linen are frowned upon. Choose shirts in "formal patterns: Oxford, plaid, and poplin are a little less formal, but perfectly acceptable. Twill, herringbone, and broadcloth patterns are more formal and nice to use if sprucing up. Hawaiian and other irregular patterns are considered too casual. Jeans are not considered business casual.  Pleated pants and dark colors are more formal, conservative choices. If you want to be on the safe side, overdressing is less frowned upon than underdressing. Pants should extend to the top of your shoe, or slightly longer. Pants that don't reach down to your shoe are considered high-water pants; pants that fold and bunch up near the feet are considered too baggy. Avoid pants in loud colors such as red, yellow, and purple. Camouflage is not allowed, neither are white pants — they feel a little too informal for even business casual. Stick with black, brown, grey, khaki, dark blue and dark green pants. V-neck sweaters work best if wearing a a collar.  Turtlenecks can be worn in combination with a blazer for a sleek look and a little bit of novelty. If you want to wear a suit coat and still look business casual, dress it down with khakis instead of suit pants. Stick to black, brown, or grey shoes. Oxfords, lace-ups, and loafers are all standards. Avoid the following items, which, fortunately or unfortunately, don't fall under the category of business casual:  Sneakers, sandals, flip-flops or other open-toed shoes. Sports shirts, sweatshirts, sport team jackets, and athletic socks. Shorts and capris. Jeans. Very tight, and hence revealing, cuts of pants. No skinny-trousers allowed.

What is a summary?
Choose shirts that have collars, such as long-sleeve button down shirts. Wear pants styles such as khakis, dress pants, trousers and corduroy pants. Consider pairing your shirt with a sweater or sweater vest. Select formal leather shoes, and don’t forget the dress socks. Study the list of don'ts.