Have a soft ball (bean bag or kush ball) that you can throw to a student after you have called his/her name and made eye contact.
Once the student catches the ball, ask a question. It can be anything as simple as, "What is your favorite color?" or, "What did you eat for breakfast?" "Using an adjective, describe how you are feeling right now?" For more advanced students, this can be more open questions.
Make sure that all of the students are listening to their classmates' answers attentively.