My first perception is that European Languages and Oriental languages like Indian languages differ in 2 very important aspects: Indian languages are totally phonetic: you speak what you write, you write exactly what you speak. There is neither pronunciation nor spelling in the Indian languages!
ALL ENGINEERING COLLEGE STUDENTS IN INDIA ARE TOLD
Successful completion positions a student to have acquired sufficient level of English-language proficiency so as to undertake studies at US universities.
I wish I had known that there is a discipline called ESP (English for Special Purposes). Examples are: English for Surgeons; English for Waiters; English for Tourist Guides, etc.
When teaching adults in a non-English speaking country, what you teach them is quite different from what you teach kids in K-12 and university. It has to be relevant to their lives, their interests, and their needs.
I had been teaching ESP for about 15 years before I realized there was a name for what I been doing.
Usually there is no textbook to follow - too many distinct applications - so you have you create your own material. It's of lot of work, but I enjoy it!
There are so many various approaches as mentioned above. I wish I had known about the Focal Skills program - http://www.focalskills.info/ earlier, as it was/is such an approach for language acquisition. Authentic learning approaches, such as Focal Skills, quickly show how much the students adored learning and provided exponential acquisition.