Spray your charcoal drawing with a fixative. This creates a thin coating over the charcoal that will prevent it from smudging. Only do this to new drawings. Older ones already will have been fixed or might be damaged by the spray.
Avoid touching the surface of the charcoal drawing. The paper may become discolored by oils from your fingertips. Mounting the drawing in a frame can protect it from touch.
Protect your drawing with a folder if it is not on display. Acid-free alkaline folders are best. Do not use plastic folders; static charge can be harmful to the charcoal.
Store your drawing flat in a dark, cool, moderately dry location. Too much light, especially direct sunlight, can cause fading, and moisture can cause the paper to curl.