As above, however we ride hills to train, not necessarily to get up them the fastest. So sometimes I'll sit and spin a hill as fast as I can, sometimes I'll sit and ride it in as big a gear as I can turn comfortably, sometimes I'll stand the whole hill. It's good to work all your modes. A rather fun thing to do is to ride all of one of your standard routes in say, a 70" gear, and try to ride it as fast as you usually do or ride it with one of your buddies who's shifting. Shows up your weaknesses pretty well.