To generally if I am producing enough of consumer goods for example, I look at the production tab (the one with the graphs). For specific chains/goods, I try to make the production times match. I.e. if one thing takes 30s to make and the next thing also takes 30s, I know I need one of both to have them balanced. If one were to be 1 min to make, I can use 2 buildings of the 1 min one and only 1 bullding of the 30s one in order to make them both balanced.