Comparison Paragraphs Organized by Subtopic Another way of organizing a comparison is not according to supporting details that are similar, but according to subtopic. (A subtopic is a main example, or main supporting idea, that illustrates the topic sentence of a paragraph. For more about supporting details, click here.)
This is an excellent packet on coordinating and subordinating conjunctions used to compare and contrast. It also has a section on using present and past tense verbs to compare and contrast events in time.