Write a paragraph that discusses a subject of interest to students. Write the topic sentence in green; the body of the paragraph in yellow; the final sentence in red. Display the paragraph. Explain to students that at a traffic light, green means "go," and red means "stop." Relate this to the paragraph. Discuss how the green sentence starts the paragraph, the yellow sentences expand on the topic, and the red sentence stops the paragraph. The aim is to create a sense of paragraph structure and show how the topic sentence fits into this.
Type out a simple paragraph of five sentences with each sentence starting a new line. Use a large font. Print copies of the paragraph -- one for each student -- and cut the sentences into strips. Have students arrange the sentences in the correct order. Discuss the results and explain the relevance of the topic sentence to introduce the paragraph. Have students write, type, print and cut their own paragraphs. Tell them to exchange their sentence strips with a partner and put the sentences in order. Again, discuss the importance of the topic sentence.
Type a simple five sentence paragraph. Note the topic sentence elsewhere and delete it from the paragraph. Print the remaining sentences and give a copy to each student. Have each student write a topic sentence. Then, have them match their results with the topic sentence you deleted and discuss.
Choose a subject that is familiar to students. Have them write what the subject is about and what is important about it. Then have each student create a list of words associated with the subject. Tell students to choose the words from the list that sum up what the subject is about and why it is important. Finally, have students put these words into a topic sentence.