Most of the time your stained glass can be easily brightened by dusting with a dry cloth or soft brush. If you need to remove any soil, I recommend Kwik-Clean, which will buff and shine the glass as well as the metals. This cleaner will also remove "White mold".
To polish and protect your stained glass, especially if you live near the coast or in a humid area, try a product by Clarity called Stained Glass Compound or Kem-o-Pro. This compound is specially formulated for the metals in stained glass work (lead, tin, copper, zinc, etc). Carefully and gently buff on, let it dry and then buff off. Frequency of cleaning depends on where you live. Closer to the coast, the more frequently it will need to be polished. This compound protects the metals from corrosion, evident by the presence of "white mold" on the metal. Be sure not to rub too hard, as this can damage patinas present on the metal.