There are a lot of articles on how to decide what cadence you should use for hills. Each person is different. This article was a in recent RoadBikerRider newsletter. Here's the start:
7. Try This on Your Next Ride o^o o^o o^o o^o o^o o^o
Take Testa's Test to find your best climbing style and cadence.
Max Testa, M.D., is a former pro team physician who now directs a sports medicine clinic in Davis, California, owned by Eric Heiden of speedskating and cycling fame.
According to Testa, the key to discovering your most-efficient cadence is to pay attention to what happens when you're about to blow on a climb.
"What fails when you're trying to keep up on a climb?" he asks. "Do you shift to a lower gear and spin fast because if you go to a bigger gear and grind your legs die? In that case, you need strength. But if, when you use a smaller gear and spin, your breathing goes out of control, you need more cardiovascular conditioning."
Try Testa's Test when you're doing hill repeats:
The test is at:
http://www.roadbikerider.com/255e.htm