I actually use three different approaches.
Lyrics first when I have no music except in my mind. I then publish them as such so maybe someone sets them to music.
Lyrics written to music when partners send me their music. Here I insist on havin a vocal line (sung nonsense like "nanana" or so).
Lyrics invented on top of a chord progression - actually a complete backing track - when I create my own music (topline writing which I refuse to do for others because I'm not a singer except when I record my own homemade stuff).
The results differ a lot. When I just write lyrics they tend to be more poetic or better structured and phrased. When I write for others my words just serve their music (attitude, rhythm...). The ones that I'm most proud of are the ones that support the music best like these:
let us party on the beach
let us party in the streets
let us party every night
let us set the nights alight
let us feel the throbbing beat
let us feel the body heat
let's be hot or raving mad
let's be free and get on bad
The tune (of the chorus) has a driving, hammering rhythm and is the same for each two lines, hence the AA BB rhyming. A pity I may no longer provide the recording of the demo. But you may get the idea: not much imagery, no story-telling, just mimicking what the music does.
Cheers,
Bernd
/\THIS/\
This is a very similar approach to how I approach lyrical writing.
Also, I like to start a song from scratch with zero melody.
What I do is, I begin to write down potential lines and general ideas for the song.
Than, I break down the syllables into parts as I am writing trying to discover as many possible different ways to sing the line as possible
Once, I get a vocal arrangement that I like, only then do I begin to write the rest of the song based on the melody I just created. (The melody is normally very easy for my composer/guitarist to write a riff or melody under, because the vocal line has been established and can be heard.)
Lastly, I intend to like riffs that are double the beat of the melody I'm singing on. So, instead of singing on the "beat" I'll sing in between the beat. Doing so doesn't change the vocal melody I wrote the song in, because in essence I am still on beat, the listener is just hearing more music when I'm not singing. This gives me the luxury of accelerating the vocal progression if I want to reach a climax somewhere in the song.
This concept also works well in reverse. Starting really fast and than slowing the song down towards the end for a more rhythmic, driving feel. (Hopefully, I'm articulating this somewhat intelligently. I'm super tired and it's kind of hard for me to explain the concept without writing a book.)
Keep in mind I tend to lean more towards Metal and Hard Rock when I am writing for myself.
Finally, I try (TRY) not too nitpick over the specific lyrics in the songs until I get a vocal progression.
To say I am not normally a "free flow" writer would be an epic understatement. Although, I do employ that style in my songwriting to try to stay as diverse as possible.
But that's me.
Joe. H