Read and summarize the text. Read the section of the text you are meant to respond to, making notes as you go. Read the text a second and third time, until you are able to orally summarize the passage. Make notes of the most important elements of the argument and any critical responses you have.
Make critical notes. Once you have a summary of the argument, write critical responses to what you read. Critical does not mean negative. Critical means that you are not taking the author at their word, but are thinking through what has been said; what it means and why it is important, or not; how it makes you feel and what it makes you think of.
Make an outline. Organize the outline for your response, taking into account the requirements of the assignment and any guidelines, including page or word count. Include an introduction, body, conclusion and relevant sub-sections. Make sure your body includes a summary (which is usually brief) and your critical reflection.
Write your essay, but focus on your response, which is the most important part of the essay. Your response should be based on your notes. It should discuss how the piece made you feel; what it made you think of; where you think the author was strong and where you think he or she was weak; and, perhaps, how you might have approached the topic differently. You might also include any gaps that the text contained, as well as factual errors or weak interpretations it might have advanced.
Edit. Once the essay is finished, proofread it. If possible, read the paper aloud to catch awkward or unclear passages. Have a friend or colleague read the paper for a fresh perspective.