I have a few different ways of marking up a text. In one approach, I make a small vertical line in the margin next to a line I find significant. Sometimes that

I have a few different ways of marking up a text. In one approach, I make a small vertical line in the margin next to a line I find significant. Sometimes that vertical line extends down a few lines to mark a longer passage. If it's really important, I add a second line, and sometimes I'll even add a third line. For many books, this is just a way of mentally noting something and letting it go enough to move on. But if I end up wanting to write a review of a book (usually a blog post, not a bookstore review), I just skim through these marked up sections. That's usually enough to guide my write up. The triple-marked sections usually end up quoted in the review. I also write a capital R in the margin next to things I'd like to research further. Sometimes I put a question mark next to a section I'm skeptical of.