The very first thing I do , if I know my subject, is start with "10 Nouns." I make a list of all the nouns that are relevant. Then I find rhymes to those nouns. Non of this has to make any sense at the moment. Then I find "10 adjectives" and find rhymes to those. Then I find "10 verbs" and find rhymes. If you just have 10 nouns and 10 adjectives and 10 verbs you have a thousand possibilities, and we are not including the rhymes. Now pursuing the possibility process, ideas and sentences will spring out of this potpourri of verbiage. It's amazing how one can start with just words and end up with a coherent story with metaphors and rhymes. Try it and see what happens.
That's my story and I am sticking to it!!
The Creative Mind