The easiest way to remember how to go up and down stairs on crutches:
the good go up, and the bad go down
because, when you are bombed on painkillers, it can be a little tricky trying to figure out which foot to start with.
I always found it easier going up and down stairs with both my crutches, rather than trying to carry one. Especially when I was in the house with wonky bannisters.
Other main tip: get some padding, and some cotton or gauze wrapping on the handles of the crutches, otherwise you'll get sticky and sweaty and blistered to hell and back. It's hard to walk with shredded palms. (Tubigrip, on top of foam was the best combination for me.)