If you have children, you probably have had crayon on the wall. To remove crayon marks easily, spray with WD-40 and wipe away with a paper towel. Follow up with a soft cloth and a solution of hot water and dish washing liquid, washing in a circular motion.
July 1, 2010:
Tree sap can be a problem on wood decks. To remove it, apply mineral spirits with an old rag, rub and wash off with dish washing liquid and hot water. Rinse well.