On a lot of the hills around here I find myself going in and out of the saddle to climb. Sometimes too, to give my quads a break, I instead of mashing the pedals, I pull up and it works the muscles around my hips more. A lot of these are steep and long, so I try to keep a high cadence until I get towards the top and then try to accelerate at a point where I know I won't totally burn myself out. I'm quite inexperienced, but I do love climbing hills, the bigger they are, the better!