Colleen Kennedy has a nice primer: https://www.academia.edu/35101285/Creating_a_Commonplace_Book_CPB_

It may also help to have an indexing method so you can find things later. John Locke's method is one of the oldest and most compact, though if you plan on doing this for a while, having a separate book for your index can be helpful. You can also create your index using index cards the way that Ross Ashby did; see: https://ashby.info/index.html

For John Locke's method try: - https://archive.org/details/gu_newmethodmaki00lock - https://publicdomainreview.org/collection/john-lockes-method-for-common-place-books-1685/

If you're into history, development, and examples of how people did this in the past, Earl Haven's has an excellent short book:<br /> Havens, Earle. Commonplace Books: A History of Manuscripts and Printed Books from Antiquity to the Twentieth Century. New Haven, CT: Beinecke Rare Book and Manuscript Library, 2001. https://www.oakknoll.com/pages/books/99718/earle-havens/commonplace-books-a-history-of-manuscripts-and-printed-books-from-antiquity-to-the-twentieth