It won't be hard to find a delicious bowl of phở (pronounced 'fuh') in Vietnam. Just look for a bunch of people sitting on plastic stools with their heads buried in bowls. A beef or chicken broth is cooked with a variety of spices including star anise, cinnamon, roasted ginger, roasted onion, cardamom, coriander seed, fennel seed, and cloves. Fish sauce is added near the end. Rice noodles are the filler -- in the north part of Vietnam they tend to be slightly wider. Beef or chicken is the protein (beef is generally more popular). It will usually have onions in it and Chinese chives sprinkled on top.
Start by tasting the broth. The flavours will make you really appreciate the several hours it took to cook. Tear off some leaves from the pile of greens that come with it. Thai basil, the one that smells like black licorice, compliments it really well. I usually dump all of the bean sprouts in. If you like spicy food, add some of the fresh chopped chili pepper, chili paste, or chili garlic sauce. The fresh chilis are the hotest of the three - it won't take too many of those to make a big difference. Squeeze some lime juice in it for a little tang. Fish sauce is usually available on the table as well. Maybe you like it sweet -- if there's a bottle of brown sauce that's hoisin, a Chinese BBQ sauce, it'll sweeten the broth. Vietnamese food is all about customizing to your taste, and pho is fantastic for that.
When you're happy with your broth, grab some chopsticks and a spoon -- it's time to eat. I like to fill my spoon with broth and use the chopsticks to pick up some noodles and meat then place them on the spoon. That way you can customize every spoonful. Experiment with different combinations. Broth, noodles, meat, with a small leaf of Thai basil on top works for me. Pho makes you really think about what you're eating, it is fun to eat and, best of all, it's delicious.