All throughout my college career and the beginning of my teaching career, I never had a good system for keeping track of research–after all, my experience was in composing instead of research.
Within the past couple of years, I’ve finally figured out a system that works for me: Index cards.
As I read through books, I mark particularly interesting passages by earmarking pages and margin notes. Getting over the idea of writing in books took a while. When finished, I copy the passages onto index cards, note the author/title/page number, and give the card a sequential number.
I’ve scanned in the first hundred, mostly dealing with creative research, and they’re available at: https://ip.vanderburg.io/files/document/F7D4AAFB-6A53-4102-BF27-70392AFEBDAE/