the most effective thing for me was working in a portrait studio for almost a year.
SEEING and HANDLING beautiful negatives and karsh-esque portraits, and then
working with someone to become a better printer. and then ... processing film and making prints
for 9 hours a day
i never really have gotten much out of technical books, not that i don't have any, i have a handful of them
but the physical objects did it for me ...
( not that you can see much of that in the things i tend to post here on apug )