Sweep the stairs with a dry dust mop to keep the stairs clear of dirt and debris that can scratch the surface. Use a dust mop that is not pre-treated with a chemical cleaner, as the chemical cleaner can permanently stain the granite.
Clean spills on the granite stairs by blotting the liquid with a paper towel. Avoid rubbing the paper towel against the stairs, as this can shred the paper towel and spread the liquid.
Wet a sponge with warm water, and wet the surface of the granite floors. Apply the stone soap onto the sponge, and gently buff the soap into the floors to create a lather.
Rinse the sponge with warm water, and rinse the floor with the wet sponge.
Blot the granite surface dry with a dry cleaning cloth to absorb moisture from the stairs.
Protect the stairs from scratching by placing a non-slip stair covering over the stairs. Remove the stair covering weekly and shake it out to remove dirt and dust.