I've seen some comments about concern with not getting all the shampoo (or whatever cleaner) out of the carpet can make it get dirtier faster.
The theory is that there is the cleaner residue in the carpet and when it gets wet, it activates the cleaner again.
So, if you get in you vehicle with wet shoes, it activates the cleaner and the dirt on your shoes gets cleaned off and into the carpet.
Anyone know if there's much truth to that?
I only bring that up because MidnightNarwhal mentioned using the cleaner and wiping with damp towel.
I don't mean to point fingers, just thought it might help with optimum cleaning methods.
Oh, and to answer the original question, unfortunately I've only 'shampooed' the carpet in my Foxbody one time (few years ago).
I've never done that in any of my other cars, mainly because I don't have an extractor.