Find a comfortable place to read your novel. It should be cozy, quiet and free of distractions like televisions or video games. Set a blank notebook somewhere nearby where you can reach it easily, as well as a pen or a pencil. You may also wish to include a set of blank Post-It notes for marking passages in the book.
Begin reading the novel. As you read, be aware of how much or how little you are enjoying it. Ask yourself why you like it or don't like it, what specifics aspects speak to you, and how they make you feel. You should also ask yourself how well or poorly the storyline is developed, how believable the characters are, and how adroitly the novel touches on deeper aspects of the human condition . Write down your thoughts in the notebook, and cite the page if appropriate it in order to refer back to it later.
Re-read your notes and organize them into basic areas of thought . Write down bullet points on the main notions you wish to convey in your critique: an overall discussion of what you feel the novel achieves and why.
Prepare a basic organization for your critique. Many critiques adopt a five-paragraph format: one introductory paragraph, three paragraphs discussing the substance of the novel and a final paragraph wrapping things up. You can adjust your critique to make it longer or shorter as you wish.
Write the first section of your piece. Introduce the main points you intend to make, as well as mentioning the novel's title, author, and basic summary of the plot.
Develop the central arguments you wish to make about the novel in the center section of the critique. Avoid plot summation or similar acts of regurgitation such as character traits. Instead, discuss the larger points you believe the book made, its comparative success as a story and the way you believe it succeeded or failed at its appointed task. In each case, use evidence to back up your arguments: don't just assert, but cite passages in the novel or other resources which support your assertions.
Conclude your critique by reiterating your main arguments and closing it up as elegantly as you can.
Set the critique aside for a period -- anywhere from a few hours to a few weeks, depending upon the time you have -- then go through it and edit it. Tighten up any rambling parts, correct any grammatical errors, and revise any sections which sound awkward or inarticulate. If you have someone you trust with writing, show the critique to him and ask for his opinion.