One problem for ESL teachers is that we can become complacent and start to take shortcuts. One day, part way through my career, I realized that this was happening to me.
I was teaching a TESL methods course to American university students who wanted to teach ESL. During one class, a student asked me what to do if some students aren’t doing the assignments or not doing them seriously. I told them that the most important motivator is to always introduce an assignment with an explanation of its purpose and how this assignment will help them in the short- or long-term future. WAIT! I suddenly realized that I had become lax in doing that in my own ESL classes.
For a dozen years, I had had the good fortune of teaching at colleges in Asia. For the most part, the students there were diligent about doing whatever I assigned without question. I soon fell in the habit of just tell them what the assignment was when I introduced it.
For example, in a Writing class, I might say, “We are going to do some practice with dramatic introductions. Look at pages 17-19. There are eight introductions. Two of them are dramatic. After you read each, you will identify which are dramatic.”
Or for a grammar exercise, I might say, “We are going to practice the most common places to use commas in sentence. Look at page 194. Let’s do the first exercise together.”
Or for a conversation activity, I would say, “Today, you will work with a partner and give directions to each other to find places on a map.”
In this 
Common Sense Teaching ESL 