Choose a comparative topic. Common examples include topics such as traveling by plane or by car or a comparison between PC or Mac computer users. A comparative essay doesn’t necessarily dwell on differences, but can highlight similarities as well. Choose a topic with differences or similarities that are easily understood.
Make a list of the comparative differences or similarities for the topic. In a notebook, list the differences and similarities side-by-side. Mark off which differences and similarities you want to further examine in the essay.
Choose a thesis. Make a statement about the differences and/or similarities in the topic. Argue why readers should be informed about these comparisons, such as why and how buying a used car is better than buying a new car.
Write only what is relevant to the thesis. There may be many differences and similarities, but only include those that strengthen the essay's argument. If there are differences and similarities that provide a counterargument to the thesis, include them--and then argue why the thesis is still relevant in spite of them.