Brainstorm your reactions to the topic. For example, if you are writing your reactions to a story about the death of a spouse, ask yourself how the story made you feel. When answering this question, start writing down your thoughts. It can be as simple as a list of emotions, such as confused, depressed, angry or relieved.
Answer a few other questions about the reaction paper's topic. Write down why you are or are not interested in the subject, what you have learned as a result or what other questions you might have. In the story about death, you might find that you were interested because the character's reactions were similar to yours the first time you faced death. You might feel you learned that you are not alone in your feelings about death, and you might have more questions about how others deal with the death of a spouse, as opposed to the deaths of others.
Examine what you are reacting to more carefully. With a piece of literature, for example, you can analyze what you think the author's intentions were, how convincing the writing was, how affected you were by the emotions of the characters or whether the story offers multiple viewpoints.
Talk about the basics of what you're reacting to in the first paragraph of the reaction paper. For a fictional story, the basics might include the author, title, genre, topic, author's motive and author's thesis. The motive and thesis might depend on your interpretation.
Use your brainstorming ideas from Steps 1 through 3 to write the body sentences for the reaction paper. Each paragraph should focus on one idea. For example, one paragraph about a reaction to a story can talk about the character's emotions and how they made you feel, while another discusses other questions you want answered.
Add details from what you are reacting to so that you can back up your claims. For example, if you feel an author's writing lacked emotion, include a few examples from the text that demonstrate emotionally charged situations that fell flat for you and needed more emotional description.