Stains starting with O
Oil
Sprinkle baking soda on the stain to soak up excess oil. Rub the stain with liquid dish soap. Wash in the hottest water suitable for the garment.
Oil paint
You can remove fresh oil paint stains with turpentine. Old, dried-on stains, can be smeared with mild soap and soak for about 10 hours. Then you can scratch away the soap and paint with the blunt side of an old knife. Then wash it.