What do I mean by writing labels in the margin?

When I read primary sources, the list below is what is going on in my head and in my margins.

I DO NOT do all of this all at once.

Choose one thing you really like and stick with it.

I really like to summarize/retell what I read.

And I really like to speed up/slow down. Meaning, sometimes I skim details that don't seem important. I'm always looking for the main idea.