I spend a great deal of time planning my classes. I try to anticipate who may be coming to class, what limitations individuals may have, what conditioning issues particular students have, what kata is appropriate for the majority of the students to focus on. I consider what events the group needs to prepare for, and what we may have neglected to practice sufficiently. I keep track of what we have covered during particular classes, and who has attended. Without these notes a great deal of this work would be wasted.
I have been to countless classes in which the instructor seemed to be just clocking in and giving a canned class. I care too much to do that. I am not a great teacher or student of karate, but I would be far worse if I had not kept notes on the classes that I have attended. The notes, just outlines really, give me a chance to reflect on what worked for the instructors and what did not. I can revisit my notes and think about where my performance or understanding was lacking and make a plan to correct those issues. I continue this habit as an instructor, keeping notes on the classes I teach. This helps me move the group forward, rationally building on previous classes.
I can not imagine spending all of the time, money, energy, sweat, and blood that it takes to get even moderately good at karate without making sure that I was as prepared mentally as I was physically. It is no more appropriate for a student to show up expecting to passively absorb the material than it is for an instructor to be unprepared for class. Bring a notebook and pencil to your next class and do not leave without taking notes about the main points covered in the class; your own performance issues; any injuries you discovered, dealt with, or developed during class; things your classmates did well or struggled with; and any questions you may still have. I think you will be surprised by how rich a resource you will have developed after even a few short months.