The first vital step is to read the text. The next step is to summarize the text. Annotation is used to simplify the text. The annotations can help you with a formal analysis in terms of identifying any patterns such as repetitions/rhythms. It is important to look at the various devices and techniques that are being used so that you can write about their purpose and what kind of effect they can bring. Another part of commentary is having to do with making connections with specific topics in the text and topics in the whole work. Within this, you can also include how this issue thematically relates to other contemporary works and influences from previous or later works. Overall, your commentary should be about the reason for your claim, and it needs to be beyond the main idea without having to restate it word-to-word.