Good lyrics can make a decent song great, and writing them should be a priority. However, sometimes a lyricist will feel that they are out of ideas, and need some creative ways to get the juices flowing again. To that end, here is a good way to write fresh lyrics and create new ideas.
What is needed to begin is simply a theme of some sort. This can come from either the music itself, or just a vague concept. What is needed is a blank sheet of paper and a pen. While considering the theme, simply begin jotting down anything, and everything, that comes to mind.
Do not be concerned if any of it sounds silly or ridiculous, the point here is to not think about what you are writing down at all. This is called free association, and it is a way to tap into you subconscious for good ideas. Just write down whatever pops into your head and do not question it.
After the page is full, stop writing and look over the mess. These are your lyrics. You can begin arranging and rearranging the words and phrases into coherent lines, and see how they look and sound. You may be surprised at how well many of them fit together. Mining the subconscious for lyrical treasure is a key to writing great songs, and this is one way to go about it.