I prefer to walk my bike up and down the stairs, especially when it has panniers on it stuffed with locks and other heavy items. Up stairs is a no-brainer: just do it. Down stairs can get out of control: the trick is to use both brakes (front's especially important) and stay a steps or maybe two above the one the front wheel is on at any given moment. As you're taking a step downward, go lighter on the front brake to let the wheel turn and bike drop a step down - and lock the front wheel right away to prevent the bike from rolling further down faster than you can walk. With some practice it's actually quite easy to do and I don't have to kill my back carrying 50+ pounds of bike+load on a shoulder.

It should be possible to stop just before the door, hold the brake with one hand and open the door with another.