Do your carpet stains return? If so, this means that the spill has seeped down into the bottom layers of your carpet and padding. To prevent this from happening again, place an old towel over stains and then place a heavy object on top of the towel. This will weight the towel down and pull the excess liquid out of the bottom layers of your carpet.

Source:http://www.cleaningtips.com/tips/house/carpet-cleaning/carpet-spot-removal.html