I find that it is often easier to put words to music, than music to words... I have crafted a few pieces of my own poems and thus put music so, but rarely...If you do write a poem and intend it to be a song, you must have a clear vision of chorus, lulls, and a bridge. Note that a bridge is not always necessary, however it is often included and ads great diversity to any piece. I play drums and piano, my brother plays guitar, and my sister plays violin, sometimes piano as well so we've dabbled in song production. Also, you can make a tune in your head, and write words to that tune signifying inflection as well as how long you hold out vowels and that will help you retain a certain idea of what you had in your head if you forget. I do that quite often as my memory is very short-term.