I have a steam cleaner and a wet vax extraction machine,the steamer hardly ever gets used apart from realy dirty ingrained plastics.

I find extracting is by far the best way,as above use with a stiff brush and go over the car a few times and you cant go wrong.

If you wet a stain on a seat it will dissapear untill its dried, so you do have to be methodical in your technique hence brushing and going over it a few times.