Thoroughly coat everything inside the caliper with anti-seize. Not grease, anti-seize. The caliper body, the sliders, the piston, the works. Then reinstall the pads and spring.
IME corrosion on the sliders causes the pads to stick and not retract, thus causing the brake to drag. The pads also corrode to the piston, which makes them hard to change. An ounce of prevention...
Thanks for the tip !
I just picked up the disc brake Friday, it's still in the box so the advice is timely. Sticking brakes and fused pads are exactly the sorts of problems I had with the cantis. I had hoped that because the brake mechanism was located farther from the rim and the fender that it wouldn't get quite as much crap thrown on it.