I always write the music first and lyrics afterwards, but some people like to think they can just write something and have someone else fit music to it later.
I usually make a beat, just let the emotion tell me what to write about... then it's a wrap.
But also, I keep a rhymebook on me and write down good lines that I think of throughout the day and usually insert those when I'm having writer's block.
But then again, I've also wrote whole songs before making the beat... but I think it's hard as hell that way for some reason...
I have to get the rhythm down first before I can craft any lines. Tweaking is inevitable, but without any idea of how the words will complement the beats I can't ensure it will flow well.
Of course, like everyone should I write lines everyday that don't necessarily have beats in existence, but suggest a flow anyway. The basic ideas in those lines can be played with later.
but really, i could have a whole song in my head, with the exact way it should sound, beats and all, and if i try to create those beats, it's as futile as trying to take a picture of the two moons you see because you are way drunk... it's just not happening...
such is the futility of my effort so far... Especially since i'm not releasing shit without being happy with it... I need a solid marriage between my rhymes and my beats...
When it comes to Hip Hop for me, I usually go lyrics first, as I can usually fit my lyrics to any which beat, for other genres it can go both ways, sometimes you need to write music before you can come up with a concept for what it's about, and sometimes you have an idea for lyrics, and then you can just fit the music to your vision. Either way, to each their own