Use the slip-box approach to take notes

Set up your slip boxes to keep notes.
You can use any two regular boxes as your slip-boxes if you prefer writing your notes by hand. You can also use an app such as Zettelkasten if you prefer typing.

Keep objective notes with bibliographic information in the first slip box.
Write bibliographic information on one side of an index card and brief, objective notes about the information and its content on the other side. Keep these cards in the first slip box.

Keep your thoughts and ideas about this information in the second slip box.
Write your comments, thoughts, and ideas about the information you have stored in the first slip-box. Think about how that information relates to your thinking and how you can apply that information to different situations in different contexts. These comments, thoughts, and ideas should be written on one side of the index to make them easier to read.

Number the notes to link them with each other.
Write a number on the notes to identify them. If a note numbered “22” provided context for another new note, the new note could be numbered “23”. If note “23” already exists, then you can number the note as “22a”.