One student shared with me that during the theoretical class, he was copying everything written on the blackboard, and had no time to follow what the teacher was saying.
I did this too. Many people do this too. But unless you have no other resource (like no lecture notes or no books), this is a very ineffective way of making the most of the theoretical class. You will learn little, understand not much, and be unmotivated. And then you need to spend a lot of time at home assimilating your transcribed notes.
If you have lecture notes the best is to prepare the theoretical class by:
(1) Revising the content of previous classes;
(2) Reading in the lecture notes what is coming in the next class. Try to understand as much as possible, and take notes of your questions or any unclear points.
Then, during class, do not copy the blackboard, instead try to understand as much as possible. Copy only when new material, information, or examples are given. Sit there, listen, and try to understand as much as possible. See if your questions are answered during the explanation. Try always to be active and not passive.
Even if you only devote 15 minutes to reading the lecture notes ahead of the class, it already gives huge benefits. You will understand much more, much faster.
Adaptation from: https://just-out-of-curiosity-merino.blogspot.com/2023/03/coaching-1-taking-notes-in-class.html
Other tips:
If you start feeling sleepy during the class, remember that you may need to drink water! (and avoid heavy meals before a class!).
Forget about your phone during the class: do not occupy yourself with anything that is not the class. Train yourself to avoid distractions.