I take my model from clay sculpture, I get an armature on which to build. I borrow another song which gives me a metre and a rhyme scheme. I write my first verse and chorus to this structure. The rest then follows almost automatically.
I then use the same idea for a new tune.

For those who know my work, the song "Llewellyn Walking" needed a slow, processional sort of pace. I chose "Angel of the morning" as the armature. That gave me the verses.
I then took "Nimrod" from Elgar's "Enigma Variations", knocked it to pieces and re-assembled it around the words. Elgar's ascending motif gave the song a sort of forward,rising positivity.

Mostly, then, I try to build my own tunes to fit my words.Sometimes, however, a tune demands to be used.
The tune usually sung to "Dear Lord and Father of Mankind" was known to me for years only as a profoundly beautiful tune associated with radio progammes heard in my earliest childhood. It kept popping out of my subconscious and reducing me to tears. Finally, I decided that only singing it to a set of words would lay the ghosts. I wrote a set of words called "Newell Highway Anthem".

Margaret Walters sings "Llewellyn" on her latest CD "Power in a song"
and Newell Highway on "Who Was Here?"
                                       John Warner/Jack Halyard