I have playing guitar for 60 years and am a sometimes instructor, usually in an ad hoc manner at jams. I would be interested to know what topics of guitar instruction were of most value, or least value. Being pretty good at math, I always stressed things like learning scales, learning the fingerboard, transposing keys, etc. All learners tune in to something that grabs them, so I was curious what topics helped the most, least.

Btw, I play mostly acoustic folk, old time, and bluegrass, but also like to get into light jazz, big band, and light rock.