In past posts I've mentioned a big hill in my running route. I'm almost to the point where I run the full hill. Every two weeks, when I increase my distance, I also increase by 50 yards or so the amount of the hill that I run (I then walk the remaining distance). In another month to six weeks I should be running the whole hill.
On my return trip, I get good practice running down the hill. Going down a steep hill is more stressful on ones body than going up the hill. Especially on the knees.