On paper notebooks -- I keep one, too, and I tried subject grouping which always failed for me within a few months. I now write clearly visible headings and ma

On paper notebooks -- I keep one, too, and I tried subject grouping which always failed for me within a few months. I now write clearly visible headings and maintain chronological order. I often color code the headings: just underlining or highlighting the title with subject color makes it easy to find. Thid, with chronological order ingeneral, works well for me in lieu of a table of contents. YMMV.