Answer #1: Steaming sometimes helps, also teasing out with a needle if you have the patience or time to do it. --
Anon Comment
Answer #2: The method we have found best is steaming and then to lift the nap with a small fork. Use a steamer or steam iron on a medium setting and hold it a couple of centimetres above the dent. If the carpet is very fine or you are worried about damaging it with the fork then steam and rub with your fingernails or a small coin. Some rugs and carpets are not colourfast so use the steamer or spray with caution. -- Ray and Denise Devizes Comment