Well, the carpet isn't really THAT bad but I'm trying to get the smoke smell out of my truck ... I recently quit smoking and it smells like an ashtray. I don't have that problem with my car because I didn't smoke in it.
I was using my parents little green clean machine but it's kinda half-assed. I used to detail cars, years ago, and got used to the industrial machines ... Don't know much about 'homeowner' stuff...
Just dont eat in you car and keep your shoes clean and you will never need to clean the carpet. I just vaccum the light dirt that comes of my shoes. Passenger side stays clean as hell.
...but every couple months i clean the carpet with some foam carpet cleaner. I dont care about the brand cause they all work the same