It's important to stay in touch with your clients. Email clients that take classes frequently and reward them. You can use the Clients tab to see who your most frequent students are by looking at the sales column. Here is a sample email:
You’ve done a great job keeping up with your training! I've really enjoyed seeing your progress and am looking forward to seeing you in class again soon. Keep up the good work and use MOTIVATE at checkout and get 30% off your next class!