You leave blank space for the index or table of contents and add page numbers as you write the content. So algebra notes might be on pages 2-10, 20-23,43-47; s

You leave blank space for the index or table of contents and add page numbers as you write the content. So algebra notes might be on pages 2-10, 20-23,43-47; shopping lists on 11 and 19; Christmas ideas on 17-18. You can of course leave blank pages after a shopping list for the next one, but with an updated index and page numbers you can easily find the next shopping list page (you can also write "continued on page ..." at the bottom). Another very different system would be to use binders (or digital notebooks) where you can easily add pages. However, then page numbers become tricky and you lose the chronological information of what was written in which order.