This is a really difficult question, and there are a lot of answers, many of which depend on your personal style of teaching. But in my experience, this is what I've found to be most motivating for students:
There are a few things you can do to keep your students interested and motivated. Get creative with your lesson plans. Try to change things up so they don’t get use to doing thing same thing all the time. Plan hands-on activities that the students can be involved and be active, rather than just sitting in a desk listening to a lecture about whatever the topic may be.