Do everything and see everything the first year you are here. After that the novelty of the city and all it has to offer wears off and you will start to see the amazing museums and offerings of DC as tourist trap. But, if you can capture all of that in the first year you will have a better appreciation of DC and be much better at playing host to friends.
Also, don’t only hang out in the neighborhood which you live. DC has lots of great areas with lots to offer.
And most importantly, when on escalator – stand right and walk left 🙂