When we rode the Metro to visit the National Gallery of Art and National Museum of American History, I goofed when trying to buy the SmarTrip Card. The trick is to buy the SmarTrip Card first, then add money to it. Not the other way around.
The metro attendant was very helpful. He wrote up a refund request for me and split the remaining ticket we had into two so that we had enough to get to the National Mall and back.
Taking the Metro is probably the best way to get around D.C. Though traffic wasn’t bad and we were able to find some free parking, the Metro is the least stressful way to go. The Metro is also just as quick as driving.
Plus, as the attendant informed me, $14 will get you a ticket that you can use for Metro rides all day long, no matter how far or how many times you use it. Our trip from Dunn-Loring-Merrifield station to the Smithsonian station was $4.50 each. That’s $9.00 for one round trip ticket. (The tickets would have been $3.50 if I had been able to buy a SmarTrip card. Instead we used regular paper tickets, called Facecards.)
You can also pay for all-day parking at some Metro stations. You can pay to park for pretty cheap (less than $5) and ride the Metro everywhere you want to go. Some stations also have bike racks and metered spaces.
Only bad thing is pups aren’t allowed on Metros unless they’re service animals. Well, I did read online that you can take crated animals onto the Metro, but that would be difficult to do with a 50 lb. dog.