How To Wear Casual Dress For Office
First, check your office rules at human resources department for official guidelines. Business casuals differ from office to office. At a large corporation, length of skirt may differ than the skirt of any hotel staff.
Don't confuse with party attire with business
attire. If you would wear it to a party or club, you probably shouldn't
wear it in a business environment. 
Pants - Fitting and Color
Women can wear casual pants. It should not be tight and should not be flowing. Fabrics should be crisp and colors should generally be solid, navy, black, gray, brown and khaki are always good options. For the most business-like appearance, pants should be creased.
Skirts - Length and Slits
Your skirt should come at least to your knees while you are standing. Too short skirt is not appropriate for work area. While you are seated, your thighs should be covered. If your skirt is just below the knee, a slit to just above the knee will be acceptable. A long skirt should not be slit to above the knee. Slits in the center back of a skirt is acceptable to facilitate walking or for stair climbing. Slits providing a view of your legs are not appropriate for business purposes.
Shirt / Sweaters
Wear
a good-quality blouse or knit shirt. Include a casual coat, blazer or
cardigan if appropriate. Cotton, silk, and blends are appropriate.
Velvets and shimmery fabrics are not appropriate for office. Fitting
should not be tight. Cleavage view is not appropriate for
business. 
Hose
Not essential for business casual, but are recommended if your skirt is knee length. Do not wear hose in calf length.
Shoes
Should be leather or fabric / microfiber. Appropriate colors are black, navy and brown. For the most conservative look, toes should be covered. Sandals which are not extremely dressy or extremely casual might be appropriate. Chunky heels, platforms, thin straps and high heels are not appropriate. Make certain you can walk comfortably in your footwear.
Jewelry / Accessories
Wear a conservative watch. Keep your choices simple in jewelery and accessories. Avoid extremes in style or color.
Cosmetics
Keep makeup conservative and natural looking. A little is always better than none for a polished look. Nails should be clean and well groomed. Avoid extremes of nail length and nail polish color.
Purse / bag
If you carry a purse, keep it small and simple. You can also carry a small briefcase or business-like tote bag. A structured bag looks more professional. Purse/bag color should coordinate with your shoes. Leather, microfiber and fine wovens are appropriate. Canvas and straw are not appropriate.