You can also use a piece of white bread rolled up in you hand in the same manner as the eraser. Just rolled it up and make it a soft piece then rub the bread over the pencil.

If you don't have an eraser, make a paste with 2 tbsp. baking soda and a bit of water. Rub this mixture into the pencil marks with a clean, white, dry cloth.

For stubborn stains, rub the area with toothpaste (non-gel) on a clean, white, dry cloth.