Find clues that indicate whether you just need to write a persuasive essay or write an argument. For example, if there are words such as "personal experience" or "personal observation" in your essay, you will know that you can rely on it to support your argument. [1] On the other hand, words like "defending" or "critical" imply you should write argumentative essays, which often require less objective and personal evidence. If you are not sure what to write, ask your instructor.