Just sit down with a blank mind and write whatever meaningless thoughts come into your head. Some will be seeds of a plot or idea for a poem or song. Sitting and thinking, open to ideas from the subconscious, the words, "Ryan on patrol," popped into the author's head. Given those words, you could easily write a poem or song on a WWII fighter pilot, a Coast Guard cutter skipper protecting our shores from drugs, or a policeman in a small town. The point is that letting your thoughts wander is great for a poet, but you have to pay attention and take down the words that pass through your idle mind. You may generate some of your best ideas this way.