Focus Your Ideas
Brainstorm about the similarities or differences in your topics. Choose a focus from your list that gives new and worthwhile information about the topic. Rather than the obvious paragraph about the differences in color between red and green apples, for instance, you might explain how bakers would use each differently based on their different flavors. For example, green apples have a more tart flavor and so would be more appropriate for a pie than sweeter red apples, which would be a better choice for stand-alone baked apples.
Write a Topic Sentence
Create a topic sentence to explain the comparison or contrast and its importance for your overall point as explained in your thesis. As the first sentence in your paragraph, it establishes your purpose, giving the reader an idea of your content and the reason it matters. For example, a comparison paragraph in an essay about choosing an appropriate pet might use the topic sentence, "Housebreaking procedures for dogs and cats differ greatly." The reader understands from this statement that the paragraph will analyze the differences between the two types of training, a difference important for readers unfamiliar with each to learn. The housebreaking focus could be one point in a three-point thesis that also includes the differences in time investment and compatibility with children.
Develop with Support
Develop the paragraph with specific information to illustrate the comparison or contrast and how it supports your overall point. Include examples, detailed explanation, definitions and whatever other kind of support that makes your thinking clear. For example, to support a topic sentence about a similarity between bottled water and tap water, details might focus on the fact that both types of water have to meet similar safety and purity requirements. Tap water is regulated by the Environmental Protection Agency, and bottled water is regulated by the Food and Drug Administration, but the purity standards are similar. Include a minimum of five sentences of support for good development of your comparison or contrast.
Conclude and Tie Together
Create a concluding sentence to sum up the similarities or differences and why they matter. For example, a paragraph contrasting community colleges and universities to argue one makes a better choice might end, "These differences in price clearly show that community colleges offer excellent education without the tremendous debt many universities impose on students." The paragraph on price could be one point in a thesis that also notes that community colleges offer smaller class sizes and more vocational programs. Include transitions within the body to help tie ideas together as well, using phrases like "on the other hand" or for a contrast paragraph and "in the same way" for a comparison.