In reading assignments from the text, in your work on graded problems, and perhaps in other readings as well, you can practice the skill of, and enjoy the pleasure of, reading mathematics. To return to the thinking that went into the writing, one must read actively, pondering as one reads, solving problems as one reads. Reading mathematics, however, as opposed to listening to mathematics or watching someone else do it or explain it, does have some advantages. One can travel at one's own pace, take a side trip, backtrack, explore on one's own. V. Writing mathematics.
Writing can also be an important tool for learning and for solving problems.
In group work on graded problems, in study groups you form on your own, in class discussions, and when I ask you to present HWK solutions in class, you can practice explaining mathematics to your classmates and orally communicating your ideas and your questions. You can practice using language carefully and structuring oral arguments.