Depends on the ride. A lot of times when a hill is approaching on a group ride, I will attempt to conserve as much energy as possible and get my HR down as much as I can so that I have a little extra buffer when the hill arrives and people start popping out of the saddle and hammering up the hills. If I am in front pulling right before the hill, I just keep the HR up where it normally is and set the pace for the hill. If I'm riding solo, I don't really think about it much. I just ride steady.