Congrats on getting in. I've run it twice. It's a fun race.
Expo
This year, the expo is out at national harbor, which is a bit of a hike. The metro doesn't run that far, but they will have shuttle buses out there. Be prepared to wait in line at security to get in. The participants shirt is always a long sleeve mock-turtleneck. The last 3 years, it's made of a thick technical fabric. It's really nice for those really cold weather runs.
Other
If the Ags are playing, the DC A&M club usually has a watching party at Penn Quarter. It's a bar, but spaghetti is one of their meal options.
On race day.
The metro starts running at 5am the day of the race. However, the closer you get to the pentagon, the more crowded the train will get, and you may have to stand a while. It's a long walk to the runner's village with no port-o-potties until you get there. A lot of guys end up peeling off to the woods and relieving themselves.
The shuttle buses are a nice option because they send them when all the seats are filled. Plus they drop you closer to the security checkpoint to the runners village. The only downside is the line to get on the buses is long, although it moves quickly once they start loading up.
It takes a little while to get through security. This past year it was a complete cluster, and delayed a lot of people getting to the start. They actually held the start line open a little extra longer as a result. I expect they'll make some changes to it this year. They only allow runners into this area, so my advice is to have your family just go to the first place they plan to see you.
The runners village is large, and has plenty of porto-potties, but the lines can get long. If you don't want to wait as long there are some next to the corrals as well.
The corrals are an honor system, so you can get as far up to the front as you want. The road is divided, at the start. The left side is a bit less crowded. A little after the start the two side join back up. However, they split again, with the left side going on a slight diversion uphill (you may want to avoid this). Since it's a mass start it's going to be crowded for a few miles. It never really started clearing up until we first crossed the river.
The first 20 miles is very scenic and nice with trees, and monuments. After you cross the bridge back into Virginia, it's not as pretty, but the crowds are still decent, until you start approaching about mile 24. From that point it's a pretty lonely existence, until you get to mile 26, where you take on that last hill to the finish.
The metro makes it nice for people to get around to cheer you on. My friends would meet me at mile 1 ni Rosslyn, then I'd see them near the Lincoln Memorial, then again after leaving Haines Point, near the Mall, before meeting up at the finish.
Post Race
You collect your medal from a Marine Lieutenant who salutes you after placing it around your neck. Next you get your picture in front of the Iwo Jima Memorial. Then proceed to get your post race jacket, and food. It's all highly organized, and the food is pre-boxed for you, which makes it easy to carry. Once outside the finisher area, you can go to gear check and/or find your loved ones. They also have finisher's gear for sale. My advice is to have your loved ones get this for you, as the lines tend to be long. (The long sleeve shirts are much better looking than the short sleeve ones).
The worst part is transportation out of the area. The lines for most of the modes of transportation are pretty long. My last year (2013), the shuttle bus line wasn't bad. Many folks who stay in Silver City, actually elect to walk the 2-3 miles back, following the course in reverse, while getting a recovery walk in, and cheering on other runners.
