Pho 75 (with locations also in Falls Church and elsewhere) is the best pho, hands down.
Before going for the first time, here's some things to know.
First, the place is far from fancy. Just a bustling place with long tables. You might have to wait in line to get in and will be seated where there's room (usually at one of the long tables with other diners).
The menu is deceptively simple: pick the small size or the large size. Then, pick the meats. Oh, but this later decision is so hard. If you're a bit squeemish, go for flank or skirt steak. Maybe briskit. You know these things. Want to do it right? Go for tripe or another more exotic portion of the cow. Vietnamese meatballs aren't a bad choice, either. But wait! You can combine meats (do I want tripe and skirt? or tripe and flank?).
The food comes out quickly. A big bowl (even if you get the small) of soup (with one of the most pleasant scents that I know) filled with rice noodles, onions, and your selected meat(s). A plate filled with bean sprouts, hot peppers, basil leaves, and limes comes on the size. Drop in what you like. Don't be scared of the leaves, which are still on branches. Just toss 'em in.
On the table, you'll find hot sauce, vinegar, and a sweat sauce. Put in what you like.
Eat with chop sticks and Asian soup spoons. Forks are also available.
As you reach the bottom, it gets a little spicier as the spices (star anise, cinamon, black pepper, etc.) tend to settle if you don't constantly stir.
They also have a nice selection of Vietnamese drinks. The salty lemonades (with or without carbonation) are unusual, but I can't image a bowl of pho without one. They take a lemon and preserve it in salt. They then throw one of these salty lemons in a glass of water with a bunch of sugar. When it arrives, nothing is mixed (the sugar is settled on the bottom of the glass). Stir, stir, stir. For those that prefer, they also have non-salty "fresh" lemonade.
Vietnamese coffee is strong, but has lots of milk. They make it in tiny pots right at the table.
Sure, there are a few other extras on the menu, but what you're here for is a big bowl of yummy soup. Great on a cold day. Great on a hot day (if the AC is on). Great when you're feeling a little blue (the hot soup and the spices do wonders for your mood). Just go!
Too bad that there prices have gone up. Although it's still one of the cheapest places around, I miss the days when you could leave having spent less than $5. Now, you'll spend a little more (maybe $8 for a bowl and a lemonade). But, gosh, that's still so cheap for one of the best foods available in the DC area.
Pay at the cashier when you're done. Somehow, they know who you are and what you ordered.