I stay in my middle chain ring up front so as to keep up my cadence. I start to gear down in the back when my cadence falls below 70. For cyclists with faster cadence than I have, they gear down when their cadence falls below 80. If the grade gets real steep over 11%, or if it is a long climb of more than a mile and I need to conserve energy, I may ease up on my chain a bit, then shift into the granny in the front. If I have prior knowledge that I am facing a hill with a grade that is excessively steep, like over 13%, I will shift down to my granny in the front and the lowest in the back at the bottom of the climb so that I won't have to worry about dropping my chain halfway up the climb. If I didn't have prior knowledge, and find myself on a hill where halfway up it turns to a 16-17% grade, well the grade is too steep to get slack to shift into the granny, so I stay in my middle chain ring and start praying. I got up some real steep hills in my middle chain ring this year, which suprised me considerably, and even more satisfying, I passed male cyclists who dropped their chains.