Great suggestions here but wanted to add, don't forget to breathe. One of my riding buddies hates hills a) she rides in to hard of a gear b)she doesn't breathe into her diaphragm. So in addition to using your gears, remember to breathe through your nose into your diaphragm, keep expanded. Don't be afraid to stick your belly out, think of all the Tour De France racers that look like they have a beer gut, that is air in their lungs as they climb. PS - same friend kicks by butt going downhill, we know we could be famous if we could combine my ability to climb with her ability to descend