It has been a while since I was there, but I do remember that the metro was my best friend! Definitely save one day or a good amount of time for the Mall. If you wind up going to the Vietnam Vet memorial (recommended) take your time – it is easy to get rushed through with the flow of people. Take your time though. We also took the metro to the end of the line one day and wound up in old Virginia (I am from the West so haven’t seen any of these places before). Lots of fun.

All the museums are free! So just go to where the majority of them are (The Mall), and go into the ones that look most interesting to you. You could spend a whole day in each one, so it’s hard to pick.