In reply to CurlyStevo: A seemigly minor thing I do is just to always walk up steps on your toes, i.e. not putting your whole foot on the step. Whilst it's only a minor thing, if you walk up your stars 10 times a day thats a hundred reps.
It clearly doesn't work by itself and you'll have to do some of the above exercises, but even a little helps right?
It helps I regularly have to do 4/5 flights of stairs to get to lectures...