Vacuum your nubuck leather couch with a hand vacuum or upholstery attachment. Make sure to suction the cushions and the frame of the couch to get all dirt and dust. Doing this regularly will help prevent dirt and dust from setting in and damaging the couch.
Blot up any liquid spills. Do not rub them or you may spread the moisture or stain.
Pat cornstarch into any stains that are oil-based. Leave the cornstarch on overnight and vacuum it off your nubuck couch in the morning. The cornstarch should help absorb the oil.
Brush the nubuck couch with a nylon bristle brush. This will restore the nap of the leather. Do this from seam to seam using a back and forth motion.
Sand any areas that have noticeable stains with a 600-grit piece of sandpaper. Do this in a back and forth motion, without rubbing too hard.
Vacuum any dust that is created from the brushing and sanding.