I’m going to get right to it. This is a technique for studying history that actually makes sense, and it’s very different from how we did it when I was in school. One principal difference is that it is non-linear. Another difference is that it works.
First, it is helpful to become familiar with the concept of a Zettelkasten or “slipbox” system of note-taking as developed by Niklas Luhmann. You don’t have to follow all of the rules, but the rules for maintaining a Zettelkasten are well-developed elsewhere on the web. Just google it.
Now, pick any topic from any time in history that interests you, say Napoleon. Learn something about him and write a note about it. Write a slip-note just called Napoleon and label that as an “%actor” because in the study of history Napoleon is categorized as an actor. This might lead you to read a little about the French Revolution. You create another slip titled “French Revolution”. This one is an “%event”. The cards labeled things like %actor and %event are for indexing the other cards, which will contain facts or situation about those actors and events.
I call these notations such as “%actor” and “%event” annotations. That is what the symbol is. What they represent is called an aspect. The difference here is the same as the difference between the word apple and what apple means. The symbol is an annotation. What the symbol means is an aspect.
If you want to write some background information about the period leading up to the French Revolution, you might label that with “%sit” for situation. (You can make up your own aspects however you want. Using %sit makes sense to me.) I also use %des for a basic descriptive note about an %event or %actor. Or you might decide that base-level facts and descriptions don’t require any aspect labeling.
An important point here is to connect the ideas by giving all of the notes unique identifiers and linking from one note to other relevant notes. In this way, the notes grow organically in any direction that interests you, and your knowledge builds in your notes in the same way that knowledge actually builds up in a human mind—non-linearly.
Note the implied philosophy here. We do not set out at the “beginning” of some event and try to learn about it from start to finish. That is folly and it doesn’t work. We work from broad outlines to detailed knowledge, and we go into the details of something only if we want to. Otherwise, the broad outlines are enough. If a basic description of Napoleon is enough to satisfy you, then you make a simple note and move on. If you want more, you might write hundreds of notes on Napoleon.
To do this, if you are interested, you really should Google “Zettelkasten” and learn about that, because it’s important, but I don’t want to get into it here because it’s so well documented already.
PS (edit): It is important to note that giving cards a fixed ID means that they have to be kept in a certain order so you can find them again later. You cannot re-arrange them to better suit a given subject. For purposes of organization, you should use links instead of physical closeness.
For this reason, it is useful to also keep an alphabetical index of your slip-box system. But you should consider it a bad thing if you have a very large index. That means your notes are not linked enough internally. You should only need a few entry points from the index, so that from there you can kind of “surf” to the information you might want in the future.
This is basic Zettelkasten stuff, but I couldn’t help myself but to emphasize those points.