I pick a subject, I think of what words will go well with the melody that I have laid out, and I try to use clever wordplay if I can, but I never push myself too hard. Another thing that helps me is that I will play the vocal melody on an instrument, as it helps me to have a clearer idea of what the lyrics will sound like when put into practice, especially since my vocal techniques aren't the best right now but I'm teaching myself.
My music project, which I hope to expand into a full band later on, involves me writing lyrics that pertain to my own viewpoints, such as Marxism, veganism, and broader anti-reactionary themes.
I also think of how I want to structure the song, e.g., if I want it to be a typical verse-chorus-verse-chorus-bridge-chorus type of structure or something a bit more unconventional.