it was the early 70's the last time I donned a backpack. I probably didn't really know how to wear one properly back then. Of course external frame packs are completely different.

Anyway, in getting my current pack to fit right, I just started out by google'ing around. I found this youtube video seemed to backup everything else I was reading
https://www.youtube.com/watch?v=pnLCM_3RjuA

One thing I learned was that I was wearing the pack too low. Once I brought the waist belt up more on my body, everything felt much better.