Flight
You can fly into BWI, IAD, or DCA, but DCA is definitely the most accessible. If you fly into BWI or IAD, you can still get to downtown DC without renting a car, but it will take about an hour. From DCA, it's a quick metro ride on the yellow line into downtown!
Train
If you come by train, the train station in DC is Union Station. It is conveniently located downtown and is accessible by metro.
Hotel
Hotel
Hotel