Help the people get interest and continue listening. Ask questions that will help people think about the answer and also make them to want learn more.

Help the people to understand the topic. Convince them by using different-different questions that will help them understand the main point.

Make the main point them clear. Ask interesting question to show the main point. Use questions to review or go over important points that you finish talking about. Then, when you ending your talk, use question to review or to go over your topic.