As a natural product, leather needs conditioning---just as human skin needs conditioning---to maintain its quality. Conditioners add essential oils to leather surfaces, preventing cracking and dryness and adding years of use to leather sofas. For a homemade conditioning remedy, mix 1/2 cup of olive oil and 1/4 cup of vinegar. Combine these ingredients in a squirt bottle and shake well. Spray the mixture on the sofa and rub gently with a soft cloth. This acts as a cleaning and conditioning agent for leather sofas, but may stain suede sofas.
Though oil in the form of conditioning agents is good for a leather sofa, too much oil from spills or greasy foods can cause stains. In the case of fresh oil stains---such as those from greasy food containers---try dumping corn starch on the stain. Rub the powder vigorously until you feel the heat of friction on your fingertips; this heat separates the oil from the leather, allowing the starch to absorb the stain. Vacuum or brush off the remaining powder. If any oil remains, repeat the process until the sofa is clean. Similarly, talcum powder may be used in place of corn starch for this home remedy.
Water spills and condensation from cold glasses can leave water stains on leather sofas. As the water dries on the leather surface, it leaves leaves an unsightly ring behind. The quickest home remedy for a water stain on a leather sofa is---perhaps surprisingly---water. The ring stain occurs when the water leaves a point of demarcation as it dries; reduce the point of demarcation by slightly wetting the edge of the stain. Do so by dampening---not soaking---a fresh sponge in a bowl of clean, room-temperature water. Without scrubbing, wipe the edges of the stain and allow the moisture of the sponge to lessen as you get farther from the spot. Focus on letting the water dry uniformly and evenly--water that dries in one saturated spot causes ring stains.
Many common household products act as general remedies to remove stains from leather sofas. Toothpaste scrubbed on stains and wiped off acts as one solution for light stains, while non-acetone nail polish remover wipes help remove ink stains. Try spraying aerosol hairspray directly on tough stains and wiping away. Repeat the process for difficult stains.