Over the years, the frame of your house can settle, resulting in cracks in drywall. This can happen especially if the work crew seamed any drywall panels above the door opening -- a strategy best avoided. Repairing the cracks can help to restore the beauty of wall.
Widen the crack into a V-shape with the utility knife. Remove the loose drywall in and around the crack. Fill the crack with joint compound and allow it to dry.
Apply thin mesh tape backed with adhesive directly to the crack or embed moistened paper tape in a thin layer of fresh joint compound.
Apply a thin layer of compound over the tape, feathering the compound at least 2 inches on either side of the tape. Allow the compound to dry.
Sand the area smooth. You can use an orbital sander or sand it by hand, depending on the size of the repaired area and what is more convenient.
Paint the area to match the wall.