A can of simple upholstery cleaning foam is the fastest and typically most successful way. The next best option would be to make a paste out water and detergent and brush it onto the fabric using a toothbrush. Rinse the toothbrush and go over the stain, picking up suds and the dirt/stain. After you repeat this several times, you should notice your stain fading away! Personally, I just like to get a can of Resolve and call it a day!