There are several methods and machines to clean carpet. I cannot recommend just one method of cleaning because different areas and certain types of dirt or stains will require a different cleaning method rather that a “one size fits all” method of carpet maintenance.
If you have allowed your carpet to get filthy (ie. Have not followed a proper cleaning method or schedule) you will generally have the most success with hot water extraction methods of carpet cleaning. Hot water extraction is also effective on individual stains such as when a cup of coffee gets spilled. It is imperative that the correct temperatures of water and correct amounts of cleaning solutions be utilized. When you use too much cleaning solution, you have a much harder time removing the cleaning solution and it can end up attracting more dirt in the next few days after you have cleaned the carpet. I have seen this happen too often….. The most effective equipment for hot water extraction is truck mounted equipment which will allow the water to be kept consistently hot and the exhaust fumes and humidity are kept outside rather than still in the building. This method is also know as steam cleaning is one of the better methods of cleaning carpet.