I use a hill that is slightly less than a mile long and has about 3% grade. It's nice if you have an easy way to get back to the beginning of the hill and that doesn't give you too much recovery time. I don't like going up and down the same hill - don't want to irritate the people who live there, so I have a loop. But you could go up and down the same hill if it's a safe place to make u turns.
I do different things. Sometimes I try to keep my cadence really high, which means downshifting as the hill gets steeper. Sometimes I try to stay in a specific gear for the whole hill. You can focus on heart rate - keeping it at a certain level or building in intensity. Once I tried standing for the whole thing - thought my heart and legs were going to explode.
V.