 Writing a paragraph. A paragraph is a group of sentences that develops one main idea. Jessica and Carlos are shopping for a new car. They look on the internet for prices. They also read about the gas mileage. They look at new and used cars. They are excited about buying a new car. There are three key parts to a paragraph. The introduction, the body, and the conclusion. Introduction. The introduction will have a topic sentence that introduces both the main idea of the paragraph and introduces your topic to the reader. Jessica and Carlos are shopping for a new car. Body. In the body of the paragraph you will explain your topic and then write supporting sentences. In those supporting sentences, use supporting details. They look on the internet for prices. They also read about the gas mileage. They look at new and used cars. Conclusion. In your concluding sentence, you will restate your main idea and finish up your paragraph. They are excited about buying a new car. A paragraph. Jessica and Carlos are shopping for a new car. They look on the internet for prices. They also read about the gas mileage. They look at new and used cars. They are excited about buying a new car. Here are a few things to remember when you are writing paragraphs. Write a title. Indent the first sentence. Indented means to leave a space. Use capital letters. Use periods. And help the reader by using words like first, next, and finally the end.