Teaching the present continuous usually takes place after the present, past and future simple forms have been introduced. However, many books and curricula choose to introduce the present continuous once the present simple has been taught. Personally, I find this can be confusing as students can have difficulties understanding the subtlety of something that has happens as a routine, and action that takes places at the moment of speaking. Add to this the fact that continuous forms are not used with stative verbs, and you might find students confused. In any case, as with other tenses, it's important to provide as much context as possible by using appropriate time expressions such as now, at the moment, currently, etc. when introducing the present continuous form. The use of the present continuous to express future scheduled events is best left for intermediate level classes.
Introducing the Present Continuous
Start by Modeling the Present Continuous
Begin teaching the present continuous by speaking about what is happening in the classroom at the moment of introduction. Once students recognized this usage, extend to other things you know are happening now. This can include simple facts such as The sun is shining at the moment. We're learning English at the moment. etc. Make sure to mix it up by using a number of different subjects.
I'm teaching the present continuous right now.
My wife is working in her office at the moment.
Those boys are playing tennis over there.
Choose a magazine or web page with lots of activity, go through a number of pages and ask students questions based on the photo.
What are they doing now?
What is she holding in her hand?
Which sport are they playing?
To teach the negative form, use the magazine or web pages to ask yes / no questions focusing on eliciting a negative response. You may want to model a few examples before asking students.
Is she playing tennis? - No, she isn't playing tennis. She's playing golf.
Is he wearing shoes? - No, he's wearing boots.
(Asking students) Are they eating lunch?
Is she driving a car?
Once students have practiced a few rounds of questions, distribute magazines or other pictures around the classroom and ask students to grill each other on what is happening at the moment.
Practicing the Present Continuous
Explaining the Present Continuous on the Board
Use a present continuous timeline to illustrate the fact that the present continuous is used to express what is happening at the moment. If you feel comfortable that the level of the class, introduce the idea that the present continuous can be used to speak about what is happening around the present moment in time. It's a good idea at this point to contrast the present continuous auxiliary verb 'to be' with other auxiliary verbs, pointing out that 'ing' must be added to the verb in the present continuous form.
Comprehension activities such as using photos in magazines will help with the present continuous. Present continuous dialogues can also help illustrate the form. Present continuous worksheets will help tie in the form with appropriate time expressions. Review quizzes contrasting present simple with the present continuous will also help.
Continued Activity Practice
It's a good idea to compare and contrast the present continuous with the present simple form once students have understood the difference. Using the present continuous for other purposes such as discussing present projects at work or speaking about future scheduled meetings will help students become familiar with other uses of the present continuous form.
Challenges with the Present Continuous
The greatest challenge with the present continuous is understanding the difference between a routine action (present simple), and an activity occurring at the moment. It's quite common for students to use the present continuous to speak about daily habits once they've learned the form, so comparing the two forms early on will help students understand the differences. Finally, students might also have difficulties understanding that stative verbs may not be used with continuous forms.