I used to teach College students in a University as part time instructor for History and Social Studies back in my country and used to babysit and teach English to a 6 and 8 year old girls on my free time.

I do not have any technique, English is a very known language and just like any language, it must be used in everyday situations. Hence, conversing and communicating with the student is one way to practice and teach them because the on the spot correction can happen from time to time.