If you have any course materials, study them in detail BEFORE class. That way, you know what you don't know

In class, refrain from taking notes like you're scribbling for your life. Slow down and listen for what you don't know. Make important notes. Quality over quantity.

Right after class, clarify your doubts immediately. Don't feel shy to ask. There are no stupid questions, only dumb answers. Then jump into your revision of the material ASAP. I can't stress ASAP enough, as your memory and understanding of the topic will fade if you leave it for more than a few days.

Whenever you gain new knowledge on the topic, go through the old material selectively, making links between what you already know and what you just learned. The connections will surprise you and reinforce your understanding.

You'll see that there is no trick or magic involved. Just lots of hard work, consistency and gallons of coffee!