Highlight the Text in the Margin

There are some other tricks for active reading. One, of course, is to highlight important or interesting passages. There are several ways to do this. The worst is to use a yellow highlighting marker (or hot pink, or whatever color you like). The main problem with this is that you will tend to find almost every sentence to be important or interesting. As a consequence, every page will become yellow (or hot pink, or whatever). Not only does this defeat the purpose of highlighting—because if everything has been highlighted, then really nothing has been!—but the pages of your text will become damp, curl up, and be generally messy.
This technique can have other problems, too:

A slightly less messy, but equally useless, technique is to use a pen or pencil to underline important or interesting passages. I guarantee that you will wind up underlining every sentence on every page, and you will have gained nothing.
The technique that I suggest is also susceptible to this problem, but has a built-in way to overcome it, so that you can re-read the text, highlighting different passages each time. The trick is to highlight a passage by drawing a vertical line in the margin. I like to use the right margin and to make my line a right square bracket: ]. If you want to make it clear [exactly where the highlighted passage begins or ends,] you can use small square brackets in the text, as I did in this sentence, along with the vertical line in the margin. This way, even if you've slipped into the error of highlighting (i.e., vertical-lining) every sentence on every page, at least you haven't ruined the page. Moreover, when you re-read the text (note that I said 'when', not 'if' :-), you can then use a different highlighting technique (e.g., underlining) to highlight more important passages. Sometimes, I use double brackets in the margin for this second round of highlighting: ]] and underlining for a third round. (If you must, you could use yellow highlighter for a fourth round.)