The next time you buy a bottle of soy sauce, cut several inches of kombu (from the overwhelming package that I am sure you have in the house because you rushed right out and bought some in order to make my instant fish stock), and put it in the bottle along with the soy sauce.
After a few weeks of the kombu macerating there, the umami levels of the soy sauce will be heightened, the soy sauce will develop an intense depth of flavor and you will have a more velvety, richer soy sauce with which to work - both for cooking and dipping.
This post is in honor of my friend Taka who taught me this trick and whose birthday it would have been today had he not died, tragically, much too young. Remembered always, with great affection.
Original iamge from The World of Chinese "how to choose soy sauce"