I realized that I did a blog post a long time back about tips for running up a hill (my clever acronym about PU-S-H-ES) but I realized I never provided a tip about going down the hills. Going down a hill can be nearly as important as going up.
So here's the trick I use: a good runner PULLS down the hills. There's no real clever acronym to this really. As soon as you crest that hill, or enter that descent, you'll feel it. Your good 'ol buddy gravity is starting to tug at you. It's tempting to resist this force at first. You're body is tired. Letting the pull take ahold of you seems like it will make you go faster and wear you out even more. In a particularly steep hill, that pull could make you lose your balance, trip, and then you're really not sitting pretty.
As long as you don't take off at a sprint going down the hill, you won't tire yourself out. Actually, you'll gain a bit more energy back from the process because you're body will have a little bit of relief since the effort to go downhill is done by gravity. Make sure to consciously stretch your stride a bit more as you go down. This will help prevent the feeling of falling and the longer stride will help you move a bit faster too. For really steep hills, I'll even let my arms flail to the side a bit to keep my body balanced going down the hill.
Most importantly, don't be afraid to let your body react naturally to the terrain and let it pull you down the hill. You'll find this provides a great opportunity to gain some energy, keep your pace going (potentially increase it a little) and be ready to hit the next straightaway or hill ready to go!
What tricks do you use for running down a hill? I'd like to know.