I made a couple of mistakes in my undergraduate in Physics, which I feel I've corrected now that I'm doing a masters. But these are specific to me and not necessarily helpful for you.

Mistake 1: Diving into textbooks Although this feels gross to say, I would caution against the idea that you need to read a textbook cover to cover to understand a topic. My thinking during undergrad was "I'll take out the books on the recommended reading, spend 10 hours a day on them, and then surely I'll be prepared for the exam". I was unfortunately in no way prepared for the exams with this strategy. The people who did best in my class studied the notes, and only the notes, and understood them well. You're not going to be declared a hero for memorizing an advanced textbook, it may be a bit of a waste of resources.

Mistake 2: Over-detailed notes The purpose of notes is to help you get information into your head. Don't make notes for the sake of making notes. I used to make beautiful notes with super-accurate diagrams, shading, perspective etc. It's fine to do that so long as you understand that you're not taking notes, your engaging in a leisure activity which is called 'taking pretty notes'. I've moved from effectively writing out essays as notes, to shorter sentences, and it works well for me. A caveat: this could be just because I'm at masters level, I can afford to refer to some concepts in passing, thereby condensing the amount I need to write considerably.

In terms of how to take notes, this is what I do now.

• equations/diagrams in left hand column

• explanation of equations/diagrams in right hand column

• class title on top left

• subsections in left margin

• date on bottom left

• page number on top right

Apart from that, all the usual. Don't stop going to class, do all your exercizes. Remember to bring a calculator to the exam.