The first line is the DNA of the poem; the rest of the poem is constructed out of that first line. A lot of it has to do with tone because tone is the key signature for the poem. The basis of trust for a reader used to be meter and end-rhyme.
Billy CollinsYou, quote, find your voice, unquote, when you are able to invent this one character who resembles you, obviously, and probably is more like you than anyone else on earth, but is not the equivalent to you.
Billy CollinsAs soon as I start to write I'm very aware, I'm trying to be aware that a reader just might well pick up this poem, a stranger. So when I'm writing - and I think that this is important for all writers - I'm trying to be a writer and a reader back and forth. I write two lines or three lines. I will immediately stop and turn into a reader instead of a writer, and I'll read those lines as if I had never seen them before and as if I had never written them.
Billy Collins