1. Dip a white cloth (or a white paper towel with no printing) into the detergent solution and dab repeatedly, then press the cloth on the spot for a few seconds. Wait 15 minutes (it takes time to break down the stain), then soak up the excess liquid with a dry white cloth.
2. Dip a cloth into the vinegar solution and dab repeatedly, then press the cloth on the spot for a few seconds. Wait another 15 minutes. (This is an important step, because white vinegar removes residual detergent, which will attract dirt if left in the carpet.)
3. Rinse by blotting with a cloth soaked in lukewarm water. Wait one hour or until the carpet dries completely. For bad spills, place a 1/2-inch-thick stack of white paper towels over the stain after step 2, then lay a glass baking dish on top for 15 minutes.
4. As long as you see the stain lightening, repeat these steps until it is gone.