If you have time/are able to, keep a look out for parents with strollers when elevators are unavailable. Far too many times I've seen someone weighing relative safety options when trying to get a baby around the city and it is SO EASY to offer to help carry the stroller down some stairs.

If you wear a backpack during rush hour, holding it down by your side instead of on your back (or wearing on your front, though I find that awkward) avoids bumping!

Metro elevators will always smell bad. Be aware.

The circulator is a set of useful bus lines but technically NOT part of the WMATA network. Tracking arrivals won't show up in Next us but the Smart trip does work for payment