Steam Cleaning is the recommended method of maintaining your carpets and warranties by all of the major carpet manufacturers.

{Steam Cleaning is a misleading term as the cleaning is actually done by hot water. ( also known as Hot Water Extraction) The steam is merely a byproduct of the process and is produced when extremely hot water contacts cold surfaces and air.}

1. The carpets are vacuumed.
   
2. A chemical pre-treatment is applied to the carpet.
   
3. The chemical is scrubbed/forced into the carpet and allowed to work for some time.
   
4. Then (for the sake of description) they are pressure washed at (up to) 230 degrees while, at the same time, a jumbo Wet Dry vacuum recovers the unwanted debris and excess water.
   
5. A neutralizing rinse is used by the most conscientious cleaners.
   
6. Spot treatments are applied as needed.
   
7. Furniture is moved as agreed.
   
8. High powered fans are utilized to begin the drying process.
   
9. Any post treatments such as topical deodorizers and stain protectors are applied
   
10. The cleaned area is then brushed or raked to reset the nap and allow for more even drying.
    

BEWARE; many outfits only use step 4! 
Steps 1-10 are Industry Recommended and required to maintain warranties.