What makes language teaching (or any kind of teaching, for that matter) so complicated is that there is no one-size-fits-all answer. The best approach will depend on your skill set, the students' needs and desires, the institutional context, etc., etc. So I'd recommend trying many things and finding out what works in your specific situation.
A good place to start looking for strategies and techniques would be a post on the Calico Spanish blog called 29 Proven Ways to Motivate Your World Language Students
You might also find some additional useful ideas from the article Motivating Students to Study a Foreign Language from the Bob Jones University Press website.
From my own experience teaching foreign languages, I think the best advice would be to close your eyes and pretend you are one of your students, walking into the classroom. Imagine what their day-to-day life is like - what they do immediately before/after your class, as well as the rest of the day. Looking at things from their eyes, what could you do as their teacher to get them to be more motivated? What I would guess would probably work the best in your situation is to find a way to make it clearer what the practical value/usefulness of learning English is (to their career, to them having fun on the Internet, etc.)
I hope this helps!