Many people find that dye-based stains (like red wine, ink, or makeup) and pet accidents are the most difficult stains to remove from carpet. Prompt action after a spill or accident will make the removal process much easier. If you do leave a stain unattended for a while, finding a product that's effective at cleaning set-in stains—like the OxiClean Carpet & Area Rug Stain Remover—will be key.