Remove loose dirt and debris from the upholstery with a vacuum containing an upholstery attachment.
Wash the upholstery with a cloth dampened with denatured alcohol. Apply the alcohol direct to a clean rag and then use the rag to wash the upholstery surface. Blot at the surface with the rag, do not rub, as rubbing the upholstery will only work any dirt present further into the upholstery fibers creating a stain.
Examine the cloth as you go along for the transmission of any staining substance from the upholstery to the cloth. Change the cloth as it discolors from the dirt contained in the upholstery, to prevent spreading the dirt along the upholstered surface. If there is a stain on your upholstery already, then multiple applications of the wash may be necessary.
Allow the alcohol to dry. Wait up to an hour for the drying process to finish before touching the surface.
Examine any stains after the waiting period to determine if the last pass succeeded with the removal. If not, the repeat the alcohol application until no trace of the stain remains.