From Flagstaff, AZ: Take I-40 W to Williams, AZ. Then Rte 64 N to Valle and continue north (merges with Rte 180). This will take you right into the Grand Canyon National Park.
Winter views are spectacular as you may see some snow on the ground. The air is crisp and clear, the light is harsh, though. Best times to take pictures are shortly after sunrise or before sunset. Unfortunately, I did not have that luxury! I was there for one day only, and we got to the park after 9 AM. We had to leave by 2 PM (we were on a trip to a different destination), so I got very harsh light and strong shadows to deal with.