Being able to determine main ideas is crucial to writing book reports, outlining, reading social studies and science materials, and general reading comprehension. That is why the lessons in this unit are so important.The 26 exercises in found here have been designed to help develop a thinking process for finding the main idea. Students begin by finding topics in sentences, then identify the main idea in a sentence. From here they move on to finding the focus of a paragraph, writing the main idea, and finally coming up with summary sentences for books.