I try to do some preventative maintenance on my interiors when cars are first bought. I Scotchgard the entire interior and the mats. (I use the blue can for rugs and carpets) When I find a dirt or spot, usually in wifes car from herself or the baby, I immediately remove it with
Wolfgangs Spot Remover and a
small brush. (see below)
I have also found that a mixture of Woolight and water works well in removing small stains on the headliner, and other interior areas. In Cadillacs the B pillars are also covered in headliner material (presumably to make the quieter) and I love this process on them also. If they were plastic, I would clean with one of those Quik Interior Cleaners and dress as wanted with 303 Protectant of something with UV protection. Mr. Clean Majic Erasers work well on door sill plastic, but must be washed out well first or transfer some white cleaner that is hard to remove from these little wonders.
Older cars and some cars that were not properly prepped might need a hot-water extractor. Best left to a professional detailer IMO, as the smaller store bought machines dont work well at all.
Steps to remove spots on mats :
1. Vacuum -- remove all dirt/dust as possible that is loose.
2. Spot Treat --- spritz and allow to penetrate for around 2 minutes. Aggitate the spot with small brush trying not to destroy the carpets fibers (dont grind let the cleaner due the work) Wipe area following the natural direction of the carpet fibers. Use a damp rag that is not excessively wet.
3. Naturally Dry --- Allow them to sit outside in sun and air to dry properly.
4. Retreat --- A final coat of Scotchgard to protect for next spot