Brainstorming is a method of writing that enables you to open up your mind and see where it takes you.
Your text may contain questions, answers, ideas and even words or sentences that do not seem to be connected to the topic. Write everything down and then select the useful ideas when you are done.
Mind mapping gives you a chance to organise your ideas and clarify the connections between different aspects of your argumentation and your paper as a whole.
This can give you a new perspective on how to structure your paper as it allows you to see how the different notions and arguments fit together.