When you write the essay for the AP test, I would recommend that you do your planning (be sure to think about focus and organization), then write the body paragraphs.
Stream on consciousness organization is not effective.
Save the introduction until the end (as we did with the Hamlet papers), so you can be sure to include in your thesis everything you write about in your body paragraphs!
Re-read the essay when you have finished to be sure you have addressed each part of the prompt.