Remove the surface dust, dirt and other debris from the leather furniture with your vacuum's upholstery attachment.
Combine 2 parts neat's-foot oil and 1-part white vinegar. If neat's-foot oil is not available, replace it with food-grade linseed oil.
Rub the leather furniture with a clean, lint-free cloth saturated in the mixture. Start at the top of the leather furniture and work your way down.
Let the mixture dry overnight on the leather furniture. Use a clean, lint-free cloth to buff the leather furniture.
Add a few drops of non-acetone nail polish remover to a cotton swab. Rub ink and markers stains with the saturated cotton swab. Dampen a lint-free cloth with cool water and wipe the nail polish remover off the leather furniture.
Combine equal parts water and rubbing alcohol in a small container. Saturate a lint-free cloth with the mixture. Use the cloth to remove mold, mildew and other fungus from the leather furniture.
Spray non-oil hairspray on tough stains and allow it to sit for five minutes. Do not let the hairspray dry on the leather furniture. Wipe the hairspray and stain off the leather with a damp, lint-free cloth.
Saturate a chamois -- cloth made from soft leather -- with distilled water. Rub scratches on your leather furniture with the chamois. If after several passes the scratches are still visible, continue with the remaining steps.
Dampen a lint-free cloth with olive oil. Scrub the scratches gently with the saturated cloth. Rub in a circular motion until the scratches are removed.
Wipe the olive oil off the leather furniture with a damp cloth. Clean and conditioner the leather furniture as you normally would.