Much of what you see in entertainment media that masquerades for professional attire is not appropriate for a work environment. Your skirt should cover your thighs when you are seated. Showing a lot of thigh makes you look naive at best, foolish at worst. A skirt that ends at the knee when you're standing looks chic and professional. Longer skirts are professional too; just make sure they are narrow enough not to be billowing, but not so narrow that you can't climb stairs comfortably. Don't purchase a skirt or decide on a hem length until you sit in the skirt facing a mirror. That's what your interviewer will see, and what others will see when you are seated in a waiting area prior to your interview. Ask yourself whether it will be distracting or reinforce your image as a person who looks appropriate for a business environment or gathering. High slits in skirts are not appropriate. A small center-back slit in a knee-length skirt is appropriate. On a calf-length skirt, a slit to the knee to facilitate walking and stair climbing is appropriate. Practice walking, climbing stairs, sitting, and standing in your skirt with the shoes you will wear. Make sure you don't have to adjust or tug your skirt into place when you move.