http://old.rosieonthehouse.com/faqs/how-do-i-care-for-my-leather-furniture

How do I care for my Leather Furniture?

Like wood, leather can fade, stiffen and crack, so keep it away from heat sources such as fireplaces, radiators, space heaters, and direct sunlight through house windows.
Keep the leather clean on a regular basis. Leather is a porous skin and is quite absorbent. You should use a damp white cloth weekly to wipe off the surface of your leather furniture. Twice yearly, use a quality brand off the shelf leather "cleaner" followed by a quality leather "conditioner".
Never use harsh soap, detergents, cleaning solvents ammonia, or vinegar to clean stains from leather. These will dry out the leather severely and may remove the dye from the leather. Best cleaners for leather is tap water or off the shelf cleaning solution. When using water, only have your cloth "damp", do not soak the leather during cleaning because too much water can cause stains also.
Never leave newspapers or magazines on leather furniture, as the dyes from the printed material can easily leech into the leather and permanently stain it.