are you trying to clean a stain, or in general? from personal experience, I have found hiring a reputable firm (recommended from the carpet store) has been the best choice over DIY. They use less water..less soap, yet get the job done. This equates to less build up.. and the longer my carpets are clean
Try a "Chem-Dry" authorized dealers. After running the installed flooring dept at a big box, I can tell you not to try a DIY method.
I can suggest an authorized dealer if you are interested, but he is in south Atlanta.
Here's some info for you: http://www.chemdry.com/
This is the company that I have been using for 8years, they are within 20 mins of Gainesville .. recommendation originally came from my carpet vendor. If you decide to call them, do let them know Becky Sue said to call!