In reading and writing about literature, we want to look for patterns of repetition, contrast, and conflict to determine the theme. We also want to read a text critically, asking questions about the social and cultural assumptions implicit in it.
All of our writing this semester is an argument, meaning that we are trying to persuade someone of a particular position. In making claims about our position, it's important not only to provide sufficient evidence, but also reasoning that shows how the evidence supports the claim. Generally speaking, the less people agree with you, the more evidence and reasoning you need, and vice versa.
To write well, you'll need to understand the poem thoroughly, which means you should read and think about it frequently. Also, read again Critical Writing and Thinking. In particular, remember:
VERY IMPORTANT: remember to answer the "So what?" question. Often the difference between a "B" paper and an "A" paper (apart from quality of argument, evidence, and writing) is the ability to explain why your argument and observations matter. A strong introduction and conclusion will usually explain the relevance of your work to some larger issue.