Smear little transparent nail polish on surface of copper or metal buttons of a new bag, to prevent oxidation.
  

Fill the bag with clean paper filler or cotton shirt, to maintain its original shape. Then put the bag in a soft cotton bag and store it in a cabinet with little stuff. Improper extrusion shall be avoided.

Always keep the bag in a dry and ventilated place. Desiccant is available for some bags which are easy to become damp.

If the bag is wet, use a piece of dry cloth to absorb the moisture, and then put it in a dry place.

Blot dry with a clean white cloth and allow to air dry completely before reuse.