I have taken many lessons and I think that in a lesson is easier to tell what I did not like rather than what I liked.
In fact, a lesson to me is good only if I achieve what I set out for.
For example, if
- the instructor takes me to a terrain whose difficult level is below my pre-lesson expectation = VERY VERY VERY BAD
- the instructor talks too much = BAD
- the instructor talks too little = BAD
- the instructor has too many students = VERY BAD (I know it is not his/her fault as I have been there)
- does not use video = BAD
- the instructor has not sense of humor = KIND OF BAD
- the weather is bad = BAD .. just kidding!
Then, if you reverse engineer my inputs you would likely find what I like in a lesson when I get a good one.
My ideal lesson is 2-3 people of similar level and with similar purpose. If I take a private lesson, I usually take it for 3-4 hours. I like to understand why we are following a certain progression (hence I like an instructor who explains things) but I do not like to freeze while waiting for explanations and I found that I do not desire the instructor's undivided attention for that long. And I like to be pushed towards more and more difficult terrain or snow conditions.
When I taught, after listening to the reasons why each of them decided to take the lesson (Guest Centered, and someone thought I was just a renegade, uhm..), I used to explain to them that skiing is about learning the best moves in different situations and develop proper muscle memory. But, I always added, that skiing requires the use of muscle that many of us do not always exercise in everyday life. Hence, I warned them that the expectation should be about acquiring the right "tools" and practice with them together with an instructor or alone. It is that practice that makes all the difference.
A good instructor presents the progression and helps them assess the quality of their movements and can serve as a model, but ultimately success relies on the students themselves as I could not ski for them, I used to stress.
I am saying this because that is the way I am approaching my lessons. I do not go there to show off, but to learn. Then I do my homeworks. After that, if I do not show off ,I get upset and blame the instructors.