Keep them inside and covered if possible. Keep them off the ground, concrete or steel plates work fine. No armoral, or tire gloss products.... Most contain alcohol which pulls the natural oils out of the tire, hence they dry rot and crack. And one thing that helps probably more than anything, just like you and I, the tires need exercise, they need to be uses, rolled at highway speeds, so they can flex and remain pliable and flexable. You won't see many tires that roll a little every day that rot and crack. It the ones that sit around and do nothing that go bad.... Just like people.....!!