Specifics for men's business casual
Basics:
Khaki or dark pants, buttoned shirt are safe for men. Polo/golf shirts are also appropriate for men.
Ties are generally not necessary for business casual.
Shirts:
Long-sleeved shirts are considered dressier than short-sleeved and are appropriate even in summer. Choosing a light blue solid, or conservative stripes is your safest bet. Polo shirts and sweaters are acceptable in more casual situations.
Socks:
Wear dark socks, mid-calf length so no skin is visible when you sit down.
Shoes:
Leather shoes should be worn. No athletic shoes or hiking boots.
Specifics for women's business casual
Basics:
For business casual women can wear dark or khaki pants, skirts or a simple dress. For a top, women can wear sweaters, strips, prints or even a buttoned shirt. Fun summer dresses can also be worn.
Women can wear casual pants, dresses or skirts. Don't wear a formal dress that could be worn at a fancy cocktail party or a prom.
Shirt / sweaters:
In addition to tailored shirts or blouses, tailored knit sweaters and sweater sets are appropriate business casual choices for women. Cotton, silk, and blends are appropriate. Velvets and shimmery fabrics suitable for parties are not as appropriate.