[wcarss]

+1 to sketchbooks. I started using them in ~2014 and have never stopped. The tricks for me were to fold each page in half to get more columns and restrict my wandering handwriting/doodles, to find cheap books (which still have hard covers) at a local art store that serves students, and to make sure I always write the date/time down when I start a new train of thought, with a heading.

Every few years I go through the last 12-20 notebooks and take pictures, then get rid of them. I don't go back through them that much, really, beyond things more than ~6 months old, but when I do I feel like it's a goldmine.