Well, I am not sure what the perfect English lesson would be but I do know what a bad way to teach English is. Recently, I was in Russia at an English school and their method of teaching English was so bad, the students couldn't speak English.
1) Use only English and only every go into the person's native language when they are really struggling to understand a concept. NEVER say a phrase in English and then immediately in the student's language. It is important that the students require a knowledge of English to understand the lesson. If it is possible to follow the class without knowing the required level of English for the level, then the lesson is badly taught,
2) Get the students to free practice (i.e. make their own sentences and engage with 'real' conversation) in English rather than asking them to translate into their own language. Being able to translate into your own language requires a passive understanding but being able to hold a conversation in English requires an active knowledge of English. If the pupil is able to have a conversation, however simple or complex, then it demonstrates that the pupil has an active knowledge of English.
3) Be vigilant to problem areas for the pupil (which you will develop with time). If the pupil struggles over simple vocabulary, lower the level rather than just going ahead with the pre-planned lesson. Being a good teacher is all about adaptability.