learning English

I talked about learning English with my co-worker when we had lunch. To be honest, I was surprised at the topic because he always tells he is not going to learn English in the future. Also he says he doesn't need English for his bussiness. Inspite of the thought, today's he asked me how to learn English for him. For your information, his level is the kind of level that he doesn't know "am" "are" "is" are the same verb. I said to him, "you had better read illustrated book for children". But frankly I don't know what is the best way for him neither for me. If there is the best way to learn English all learners carried out the way already.