Taking a basic research approach early on may help you to start exploring facts, opinions/arguments/questions, and the relevancy and quality of sources that you discover. Each draft is an opportunity to review and sometimes replace the sources from which you draw support/evidence.
1. Facts and biographical (general and specialized encyclopedias, almanacs, [auto] biographies, etc)
2. Older, established literature criticism and theory (library catalog: books)
3. Specific scholarly "conversations" (library databases: journal articles)
4. Citing evidence (source citation: MLA 8, RefWorks)
5. Drafts & revisions (lots of support: research librarians & learning commons)