I often compose on my classical guitar. Nothing to set up. Pick it up and start playing.And take notes, on small pieces of paper, in whatever format.For songs, I usually disconnect the lyrics from the music. I create patterns of music and I create patterns of words. And then combine them: play through chords or melodies and try some of the lyrics. See what fits.There are no rules and you can always approach things differently.The musical genre is also not fixed: sometimes it's pop, sometime electro, sometimes rock or alternative. Only when I "try" do make something more progressive, I start thinking more in advance, but this usually boils down to defining rhythm, rather than melody or lyrics.I often write lyrics with an existing song in my head. This helps to keep a good rhythm and keep a flow in the text. This helps, as English is not my native language. But there is no rule stating that the song will sound anything like the example in my head.I do have a classical education (solfège, classical guitar), which helps my writing. I sometimes just write chords, while other times it's full written out scores.