I forgot to mention two things about soy sauce:
1. Lee Kum Kee Is the Chinese brand most most Asians use at home. Avoid La Choy like its the plague!!! Its not real soy sauce. It's made using a chemical process instead of traditional fermentation methods. While we Asians will disagree on which country makes the best soy sauce, we are united and unanimous in that we all think La Choy is the worst tasting "soy sauce" on the market.
2. If you can't find Chinese soy sauce, then a Japanese soy sauce type called Tamari is probably your next best choice. Tamari is made in the traditional Chinese method, so the flavor profile will be most similar to Chinese soy sauce. And Tamari (San J Brand) is stocked by most grocery store chains.
In Chinese cooking, light soy sauce is the standard. Asian recipes frequently indicate either light or dark soy sauce. If the recipe does not indicate type of soy sauce, then light soy sauce is probably the best choice.