Vacuum the upholstery regularly to remove surface soil so the dirt doesn't work its way into the fabric fibers. Use an upholstery attachment or the brush attachment on the vacuum when cleaning sofa fabric.
Combine 2 tbsp. of ammonia with with 1 qt. of water if your sofa label carries the cleaning code (W) or (WS). Use a dry cleaning solvent if the sofa has the code (S) or (WS).
Moisten a clean, white cloth in the cleaning solution. Dab the solution onto the soiled area, moistening it lightly. Work on a small area at a time so the solution does not dry out while you are working.
Blot up the cleaning solution with a second clean cloth. Turn the cloth to a clean area as it becomes soiled and blot until the upholstery is nearly dry again.