How do I cook Japanese soba noodles?

Simply put, like most any other pasta. :) Like any other pasta, make sure that the water is boiling well before you put the noodles in. Also, make sure that you don't overcook the noodles - or they will become too soft and bloated. There should be some indication on the package, but normally 4-5 minutes should suffice. When they are done cooking, you should immediately pour them into a colander and rinse them with cold water (again, to prevent them from continue to 'over-cook'). They should be served immediately. The most common ways to eat them are with tsuyu, a common soup base which can be made quite easily (roughly equal parts mirin (sweet cooking sake) and soy sauce, perhaps with a bit of dashi, if you have it). If you want to eat it in the summer style, you eat the cool noodles dipped into this strong (cold!) dashi. This is zaru-soba. In the winter months, it is usually eaten as a soup and served hot. The soup base is the same tsuyu described above, but thinned with water (or, better, dashi, if at all possible) at about a 1:3 ration, or one part tsuyu to three parts water. You can add garnishes to the soup and all the recipes can be altered to your own tastes, of course. Oh, forgot to add, when eaten cold (zaru-soba), the common garnishes are chopped green onion, bits of nori (seaweed), and wasabi, on the side. These are mixed into the tsuyu to your liking, to add more flavour. Haha, hope this was all clear. Please do ask me to clarify anything that was confusing.