My fav lyrics sound as though the melody is an exaggeration of the natural intonation of saying the lines. Write something, anything, and read it out loud and try to exaggerate the tunefulness.
Steven King says when he first writes a book he tells the story as it comes to him, without interupting the flow. Then, he comes back later and reads it, trying to understand the themes inherent in the material and the images it brings to mind. Then he rewrites the whole damn thing, changing character names, emphasising certain sections, dropping others...
I've tried it on occasion. I wrote some rather boring lyrics "won't you come down, won't you play with me"... as I got deeper into the piece it turned out to be in the voice of a stalker, and the lyrics changed to "won't you calm down, don't you shout at me" which I felt a lot less uncomfortable with. Delivered in a calm, tunefull voice it sounded chilling (to me at least).
Punchline there is, it's hard enough writing lyric, so when writing deny critical thinking. Save critical thinking for when you've got enough stuff down.
Last point: when trolling for ideas, I sometimes get some friends together for drinks and just keep notes on the flow of their conversation; or eavesdrop on people in restaurants; or buy a newspaper.
And no, I'm not famous.