Start by helping your audience become comfortable with you. Keep a relaxed posture, smile and speak clearly so your students can understand you.
Start with a question in mind that you want your students to eventually answer. Keep your questions open ended. Don't ask for just a yes-or-no answer.
Allow silences to happen; you don't have to talk all the time to be effective. Give students time to ponder your questions and they will eventually speak.
Introduce different viewpoints to get students thinking outside the box. Ask controversial questions, present problems or sub-problems or relate to your students a common experience to create a discussion.
Don't interrupt students when they are responding. Follow the question-listen-respond format for your discussions. Ask questions that clarify, provide further evidence, open more questions, link to other information, create a cause and effect or provide a summary.