Pour salt, kitty litter or another absorbent material on the stain as soon as it occurs and leave it on the stain overnight.
Vacuum the absorbent material from the carpet.
Pour club soda over the stained area, gently agitate it with your fingers for two or three minutes and then blot it up with an absorbent towel.
Mix a solution of 1 tsp. liquid detergent with a cup of mildly warm water.
Blot the stain thoroughly with a clean cloth soaked in the solution. Do not use so much solution that it saturates the backing of the carpet.
Mix one part vinegar to two parts water and blot the stain while gently rubbing it with your fingers.
Repeat the process if necessary to remove all of the stain.
Sponge the stain with clear water and use an absorbent towel to blot up the liquid.