One way to make sure you have understood a piece of writing is to write a response to it. It may be beneficial to first write a summary of the text, covering the thesis and main points in an unbiased way. Pretend you are reporting on the "facts" of the piece to a friend who has not read it, the point being to keep your own opinion out of the summary. Once you have summarized the author's ideas objectively, you can respond to them in your writer's notebook. You can agree or disagree with the text, interpret it, or analyze it. Working with your reading of the text by responding in writing is a good way to read critically.