I'm fond of the stupid saying "this song writes itself" and sometimes it feels like that, I'll start singing and playing and the whole thing will tumble out. I used to like jamming on dictaphone, haven't done it ages but. I've never found there to be a neat or single process for songwriting. Obviously actually spending time writing helps but for example I've had melodies for years and sometimes more than one set of words, other times Ive had lyrics that never adhered to music for ages, and other times the two arrive at the same time.