When drawing skirts, you have to determine the length and the width. Length of skirts varies from long (ankles), semi-long (calf), average (knee-high), and mini-skirt (thigh). As for width, only two: wide and loose or thin (i.e. form-fitting).
Above are several skirts ranging from simple to detailed. The best way to start drawing a skirt is to draw a simple outline and add details after. To avoid making your skirt look stiff, you add curves to the hem. The more curves you add, the more, in this instance, column fold lines appear.
Drawing pleats for school uniforms are quite easy. The lines are all basically straight with pointed edges unlike regular cloth which has rounded ends when folded.
When drawing skirts at the side view, just remember that the front is flat and the back has a curve for the posterior. Other types of skirts includes slits at the back for professional skirts and at the side for more a casual or risque look. There are other types with more flounces and the best way to find more examples are in catalogs or even online!