Or any student can choose one from a stack in the middle of the room, face up. One way to introduce and teach this important grammar point is a listening lesson. In this case, students may need to listen to something and choose examples of correspondence between the subject and the verb. Or maybe you`d like to find an exercise from a non-native speaker who has a few mistakes in them, and get students to choose them. Then say a topic and the student must make a sentence with that topic and its verb, and then finish the sentence somehow.