Brainstorming is an informal way of generating topics to write about, or points to make about your topic. It can be done at any time during the writing process. You can brainstorm the topics for a whole paper or just a conclusion or an example. The important point about brainstorming is that there should be no pressure to be "brilliant." Students should simply open their minds to whatever pops into them. Think of it as a kind of free association. When I say "literacy" what pops into your mind? Much of what the students will come up with will not be useful, but that's okay. Part of brainstorming will involve a selection process.