I also teach adults English, some in the framework of English study groups in the workplace, some private tutoring. The commonality is that most adults (by adults I mean after the age of 21, not schoolchildren) know what their strengths and weaknesses are by the time I meet them.

Adults are interested in FUNCTIONAL English, for use at work, or perhaps they are planning to travel internationally and need that vocabulary--checking into a hotel, renting a car, changing a plane ticket  and the like.

So the very first thing we do is an assessment of sorts, to see  how they are functioning now and where they 'get stuck.' Some have bad memories of grammar in school, others have very low vocabularies and still others still need to master the mechanics of reading. There is a high incidence of unidentified learning diabilities in this group, people who alway thought--and had been told-- that they were 'just dumb' and could never grasp English.

If in a group, I go over the results of their assessments and see what their commonalities are, English-wise, what we need to work on. There may be several levels, so usually try to use an easier edition of one of the local English newspapers  as a starting point, first teaching vocabulary and then reading a story in the paper. I try to make it a story with a bit of controversy so that we may discuss it afterwards. Grammar is taught when it helps them understand a story, not as a separate subject. If there is a workbook, we also work in that too.

(Some workplace groups have a mandate which we need to fulfill also-- to make the employee more effective by improving his English skills, etc., which I also need to take into account when planning.)

When working with individuals, I try to tailor the lessons to their needs and preferences, both in terms of stories read and in terms of larger goals. After all,  they are coming to me after years of struggling with the English language; my unspoken task is to make it enjoyable and non-threatening.