Link: http://erikdemaine.org/folding/ ; http://courses.csail.mit.edu/6.849/fall10/lectures/
If you are a beginning designer, you should realize that no design is sacred. To learn to design, you must disregard reverence for another’s model, and be willing to pull it apart, fold it differently, change it and see the effects of your changes.
Small ideas lead to big ideas; the concepts of design build upon one another.
I learned first by borrowing books from my local library and then from Robert J. Lang books I bought. But that was before the Internet. Nowadays YouTube is an excellent resource for learning some foundational folding principles, some base folds, and getting past tricky "folding bottlenecks" that were always a huge frustration for me when I was learning from books. It's just really hard to clearly convey some 3D folding steps with only 2D diagrams. For example some of Robert J. Lang's phenomenal insect models (https://www.amazon.ca/Origami-Insects-Robert-J-Lang/dp/04862...) are hundreds of steps, and it's super frustrating to get stuck at say step 130 with only 45 left to go.
Anyway, I prop up an iPad up with Youtube and work through models with my 6 year old son, and he's learning way way faster than I did when I was his age.