Beer is made through a fermentation process, and it's that same fermentation that causes the unpleasant odour that wafts from beer stains in your carpet. Left unattended, beer stains and odours will attract dirt, and the smell will just get stronger. Thoroughly remove beer stains in your carpet to prevent the odour from lingering even longer.
Place a thick layer of paper towels on top of the beer stain and stand on them or apply pressure with your hands. Change to clean towels as needed, and continue to soak up as much beer as possible.
Mix one tablespoon of liquid dish detergent with one tablespoon of white vinegar and 500 ml (2 cups) of warm water in a bowl. Stir the solution with your hands to mix well.
Dip a clean cloth in the solution and dab at the beer stain, beginning at the perimeter of the stain and working inward. Blot up the solution and beer stain with a clean, dry cloth. Alternate dabbing the stain with the solution and drying it with the cloth until the beer stain is lifted.
Wet a clean cloth and wipe at the site of the beer stain on your carpet to remove any remnants of soapy solution or beer. Rinse your cloth frequently and continue to rinse the carpet until you've removed the cleaning solution and traces of beer.
Lay two or three clean cloths on top of the site of the stain. Stand on the cloths or lay a heavy object on them to help soak up the moisture in your carpet. Change to dry cloths as needed and continue to soak up the moisture.
When the party starts to get wild, consider moving beer drinkers into the kitchen or out onto the patio in an effort to prevent spills. In a pinch, pour baking soda or table salt onto the beer stain so it can soak up the beer while you gather stain-removal supplies.