With kids in the house, you might find chewing gum or crayon stains mysteriously appearing in your rug or carpet (try finding a kid to own up to them!). For each of these, you need to use undiluted vinegar. To remove crayon stains, tackle the spot directly by dipping an old toothbrush in vinegar and scrubbing the stained area.
If you find a dried blob of white school glue on your carpet, try treating it with a vinegar and water solution sponged in and blotted. However, if the spot is stubborn, warm up the vinegar a little bit on the stove or in your microwave and sponge it in undiluted. Let it sit for 10 to 15 minutes, then scrape it away. Clean up any residue using the vinegar and water solution.