Brainstorming is the technique of writing any ideas that come to your mind without worrying too much about any logical order, sequence, punctuation and spellings. While brainstorming, one does not need to bother about the order of thoughts and the correct usage of words. Instead, one should focus on collecting as many ideas and data available on that particular subject.
Take your time to think of a topic. Collect your thoughts and start writing them down in random. Let one idea freely lead you to another related idea and so on. This collecting of information will slowly give you an approach to the content. After some more time, a few alternative approaches will be formed. The more you keep looking at the streams of thoughts that you have put on paper, more ideas will form.
Now try to arrange these ideas in a logical flow. Do not start checking for grammar yet. Just try to get a uniform flow. Now all your ideas will be streamlined. Thereafter, do the necessary editing like replacing certain words with more appropriate ones, checking grammar, usage of words, spelling and punctuation?