Shake some baking soda onto a damp sponge, and scrub the marks away using a gentle, circular motion. Baking soda is a natural, abrasive cleanser that won't do any damage to your walls or even wallpaper and should take care of minimal crayon marks.
Squeeze white, nongel toothpaste onto a toothbrush or cleaning cloth, and use it to wipe the crayon marks away on the painted walls. Toothpaste contains an abrasive agent that scrubs your walls as it does your teeth and removes crayon stains. Rinse the toothpaste away with water, and pat the area dry with a clean towel.
Erase small stains from painted walls with a standard, pink pencil eraser. Gently rub the eraser over the crayon marks to erase them until they are gone. Wipe the eraser residue away with a cloth.
Remove stains on wallpaper or painted surfaces with dry cleaning solvent. It can be poured onto a dry cloth and rubbed onto the crayon marks to remove them.