DC's Metrorail

One of the easiest ways to get around the DC metro area is on the subway.  Metrorail, usually just referred to as the metro, is part of the Washington Metropolitan Area Transit Authority (WMATA).  You pay with a card which you load with money at a station, and use that card to get into and out of the system.  There is a fee for both entry and exit, and you need to use the same card for both, so you can't share and you can't lose your card.

The WMATA's website provides a map of the metro system on its website.  It's worth clicking the "Google Map" button on the upper right to compare the pictorial metro map to the real layout of the rails.  The important point to note is that not all stations are physically spaced or located as the first map may lead you to believe.  Stations in the center of DC and Arlington tend to be close to each other, while those farther away from the busiest areas are farther away from each other as well.  If you zoom in on the map you can see several of the exterior stations have a car icon signifying the ability to (pay to) park. 

The traditonal metro card, called a Farecard has a magnetic strip and is inserted into the front of the entry carousels.  Cards with low value left can be loaded onto new cards, or may be increased at the Addfare machines.  There is a warning on these cards saying to keep them away from magnetic devices and other magnetic strips.  This includes devices like your cellphone, and is important.  In my experience the cards are very easy to wipe out, and more often than not the station managers won't be able to get them working again.  You can go to Metro Center (a stop on the Orange, Blue, and Red lines) to get your value loaded onto a new card, but this is an inconvenience at best.

I have found that the SmarTrip card is a good solution to the problem of magnetic cards.  It is a proximity card, so you just wave it above a sensor and are good to go (unfortunately, it isn't strong enough to read through my wallet).  You can load the card with up to $300, and if you happen to lose it, you can recover the funds if you register the card beforehand (so make sure you do).  It's even accepted by many other transit systems in the area, and saves you $0.25 on each ride you take on the metro.  The only downside to the card is the $5 cost.  If you're briefly visiting, it may not be worthwhile, but if you're in DC for good, or planning to return soon, it's probably a wise investment. You can buy your card online at the site above, and have it mailed to you before your move or visit (that's what I did).

The metro's schedule, price, and amount of traffic (especially amount of traffic) vary throughout the day.  The 'regular fare' is in effect weekdays opening-9:30 a.m. and 3-7 p.m., as well as weekends midnight to closing.  There is a reduced fee all other times.  Finally, there is an extra $0.20 charge during the so called 'peak-of-the-peak', which is weekdays 7:30-9 a.m. and 4:30-6 p.m.  The actual fare varies based on where you get on and where you get off.  Trip Planner can help you figure out the actual cost.  Unlike some other cities there are no month passes.  A day pass is available, with some travel time limitations.  More information about available cards can be found here.

As I mentioned, the frequency of trains also varies.  During the 'peak-of-the-peak' trains are very frequent, and you won't have to wait much more than 10 min.  They normally come back-to-back, only 2 or 3 min apart, so if you want a less busy train, it may be worth the short extra wait (see the schedule boards for exact arrival times).  During the morning there are a lot of people traveling into DC, and in the evening there are a lot traveling out.  If you can 'back-commute' (and head say, from DC to Arlington in the morning, and Arlington to DC in the evening) then you'll be smugly watching people get crammed into trains going the other direction.  If you must travel with the general flow of people, it may be worth the trouble to avoid the peak-of-the-peak travel times.

Hopefully this gives you some insight into using the Metro!  Let me know if you have any other Metro questions!