Read the subject material thoroughly. As you read, make notes of sections you have difficulty understanding as well as sections that you find particularly interesting. Keep these points in mind when you read the rest of the material. This will help you begin to develop the critical points you will write about.
Read external research material that adds to your knowledge of the subject matter. If the subject material makes specific reference to other works or schools of thought, research these subjects to better understand the perspective of the author you are critiquing. Also, consider the subject material in the context of your previous studies, especially if you have read related material. By invoking external references and drawing from their knowledge, your own critique will be more thorough and supported.
Make an outline of your critique before you begin to write it. Consider the points of interest you found while reading the subject material and think about how you can apply them to an overall critique. Use this consideration to write a general thesis statement which states the aim of your essay. Map out the rest of the essay by thinking about main points you wish to make in each subsequent paragraph.
Arrange the points in your outline so that they are best suited to construct an entire essay. That is, arrange your discussion so that each point leads into and builds on the last. If your critique is on another written essay, try to arrange the points of your essay in a different order than the subject material. This will help you to avoid summary and will also help you develop your own points in the context of your own thinking.
Use your outline to develop a full critique of the subject matter. Write from an unbiased perspective by fully supporting any points of contention you explore. Also, fully analyze all relevant points of the subject matter, as leaving out points the author made will make your critique seem underdeveloped or incomplete. Properly cite all of your references and include your sources in a bibliography.
Reread and revise your essay multiple times. The first time you revise, concentrate on the overall construction of your essay and arguments. Make sure each argument is adequately developed and leads into the next. After you have developed your essay through revision, reread it to ensure that it is linguistically and grammatically sound.