What a broad, and yet very interesting question.
Without knowing exactly what you are talking about or what the circumstances are my best answer to you is that English, or any language for that matter is best taught through immersion in that language at as an early an age as is possible. For first language learners that age is pre-birth while still in the mother's womb, and for second language learners no age is too early to begin learning a new language.
As older learners of a new language we face a more difficult challenge, but the process through which we learn remains the same.
Unfortunately, the majority of those of us who would like to learn a second language, immersion in the traditional sense is not an option. Does that however mean that we are stuck with copying grammar and memorizing phrases and vocabulary? No! In today's information age it is easier than ever to immerse yourself in a new language. This is especially true for English.
Beyond the memorization that is required at the beginning stages of learning any new language, I think the best way to teach English is to immerse any student you may have in the English language as much as is possible for you.
So much language learning happens outside of the classroom. Encourage your students to read books in English, talk to a tourist in English, or watch movies in English. Even if a movie is poorly understood the first time around a great way to independently improve your grammar and pronunciation is to watch the same movie many times until you have all but memorized the dialogue. Reading books in English also accomplishes this task quite well. In fact, reading books is also a great way for first language students to improve their own grammar and vocabulary.
In conclusion, this is a very general answer to a very general question, but its a topic worth looking further into for the specifics of your situation.