1. Store-bought carpet cleaning sprays often do more harm than good.
If not used properly, these may react with the spot and set it permanently as a stain, or even permanently discolor the carpet.
2. Get to know your spot.
All spots are not created equally. Be knowledgeable of what caused the spot and what product gives you the best chance of removing the spot without damaging the carpet.
3. Use the least aggressive method.
Common household cleaners such as laundry detergent and dish soap are highly effective at removing spots. They are also very mild and stand less of a chance of harming your carpet. For greasy spots, use a small amount of dish soap on a damp cloth. For protein spots (milk, blood, pet spots, etc.) use a detergent with enzymes. Tide original is a good example.
4. YOU BLOT THAT SHHH...uh...STUFF!!!
It may not be $25,000.00 Alpaca, but take a hint from Denzel in American Gangster and blot that! Blotting offers a better way to allow the spot to transfer from your carpet to the cleaning cloth. Rubbing a spot will only aid in grinding the spot deep in to the carpet's fibers.
5. Rinse, Rinse, Rinse!
Thoroughly rinse the cleaning agent from the carpet. You can do this by blotting the area with a damp cloth, continually turning it to a clean section.