The first thing I do is find a subject, personal or not.
Then I write down any word that comes to mind when thinking of that subject.
I organise them to get small groups of riming words. Then try to write phrases with them.
It's kinda mathematical but it works for me.
Exemple :
Subject : How time goes by too quickly
Words : Hourglass, past, futur, present, time...
phrases : As I look in the hourglass, and reflect on my past. Seeing how fast I'm loosing track of time, I need to embrace the present and make it mine.
they kinda sucks at first but A little more work could turn these phrases into good lyrics.
Anyway, breaks over, got to go