1. For a shorter work, like an essay or short story, choose a random number (n). Then pull out every nth word from the piece (or every nth word from each line, if it's long enough) and use those words in a poem.
2. For a longer, book-length work, you can add a bit of complexity. Choose two numbers (n and o). Then pull every nth word from every page that ends in o. Or stay with the single number but pull the nth word from every even or odd page, or every page that ends in a multiple of o, or some such variation. You can even go a little wild and pull every nth word and nth times two word, and nth times three word. The possibilities are endless, so just work out a system and then stick with it.
Once you have your word bank, you can use them in lots of different ways:
1. Leave them in the order they were pulled.
2. Limit yourself to only the words pulled, but change their position.
3. Add words to the word bank to write a complete poem.
It will be interesting to see if these new poems have the same "voice" of the originating work, or if they will be completely new creatures. I suspect it will depend on how many words are pulled from the source (the more pulled, the more like the source, perhaps). And will neutral readers be able to tell what the original work is from the new poem code? I wonder....