Substituting Soy Sauce can be tricky as it is a very distinct flavor. In general the best substitution for Soy Sauce is Worcestershire sauce diluted slightly with water. How much Worcestershire Sauce to use will depend on how much Soy Sauce is called for. If 1/2 cup of Soy Sauce is called for then 4 tablespoons of Worcestershire sauce mixed with 1 tablespoon water is best. For a complete guide to kitchen substitutions see: http://allrecipes.com/howto/common-ingredient-substitutions/.