I saddle soap them to remove the factory gunk then I use a product called Snow seal. Snow Seal won't clog the leather and allows it to breathe so it doesn't rot. You heat the leather either in the oven on about 200 deg or less or with a hair dryer and rub it into the heated leather. You can get it at Cabelas or Dicks. I have also seen it online.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!