Actively extract main points and important details. Be sure to understand the material before marking. If the information is new or difficult, rereading a couple of paragraphs may be necessary. Going ahead a short distance may help. Reading troublesome passages aloud may help to improve concentration.
Exaggerated expression enhances comprehension.
If unknown terms are blocking understanding, pause to look them up. Mark information that will be needed later for test preparation. Do not over mark or the purpose of shrinking a large amount of material to a manageable amount is defeated. Underline a portion at a time. Generally, read a paragraph to the end before deciding what is important enough to mark.