PARAGRAPH DEVELOPMENT: Plan before writing!. TOPIC SENTENCE. BODY. TRANSITIONAL EXPRESSIONS. CONCLUDING SENTENCE. SUPPORTMAIN IDEAS. Developing a paragraph . Unity: The Topic Sentence A paragraph deals with one main idea (topic sentence). If you are moving away from that idea, conclude the paragraph and start a new one.The first thing you must determine about each paragraph is its focus. Once you have done so, you should never allow yourself to veer away from that governing idea. .