I may see something that triggers a memory or thought, get an idea, an image, a sentence fragment, a word that pops into my head and I write it down in a pocket notebook or in the Notes section in my phone. I might think about it during the day, add to it, try to understand what I wanted to express, type it up, print it out, put it in a folder. Let it sleep. Come back to it. Maybe that day, maybe a week later. Maybe longer. Look at it. Play with the words, the lines, say them out loud. Rewrite. Put the poem back in the folder. Marinate some more. Edit. And when I'm really stuck putting it together I'll go for a walk and trust the words to find me.