For the longest time I used to start with a guitar riff, and then try to cram vocals and stuff around it.. At some point I "heard" a vocal melody and words for a chorus in my head and decided to write guitar parts around that.. after some quickie recording, I realized that song was WAY better song-wise than any of the other crap I had forced with guitar riffs.. So, I started writing like that: get the vocal melody first.. don't even need words right off the bat, although it helps.. I learned that from Paul McCartney, who used to write gibberish lyrics to good vocal melodies he came up with so that he could sing the melody to John Lennon who would write the lyrics.. I'm sure you've heard that the McCartney's original lyrics to "Yesterday" were "Ham and eggs"..
but, it is a major challenge to actually FINISH a song.. I get the vocal melody, then work out the guitars, drums, bass, and sometimes piano - without ever having even half the words.. I get all that recorded and then never finish the lyrics cuz I've moved on to the next song.. it kinda sucks.. I KNOW I would finish if I could sing good, but the good Lord did not bless me with the most ear-pleasing voice..
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..