I find that songs all come in diffrent packages. Sometimes a riff is all that is needed, other times it is a good phrase, others it is an intelectual idea that I want to express, others it is just a blinding flash of overwhelming feelings. I have come to enjoy this wide ranging variety of paths that lead to inspiration. It makes me think in diffrent ways, some calculated, some a seat of the pants romp with the muses. There is no one way to songsmithing. You just need to be inspired, however you come to that fountian of creativity.