[EnSkorSang]

I have no formula for a song at all....I find that if I write to a formula everything turns out too similar and dull. I just wait until an idea arrives, and then I set myself boundaries or limits to work within as I find a bit of pressure helps.
In terms of what comes first...lyrics or music, it is easier to write music then lyrics to it, but often writing lyrics first gives a better song as the other method forces you to fit the words to the music which can give some clunky lines and you dont have to be so inventive with your melodies.
You missed out a 4th method aswell....when you do both together...e.g. many of the songs i have written have started from a lines of lyrics which arrived complete with melody, then i would write another line and do the melody or vice versa. A few times a whole song, lyrics and everything has just been there.