-Study to learn and understand - Comprehension is the most important thing. You should attack every class like, "This is my opportunity to master this subject". If you follow no other piece of advice, at least follow this one and you'll be okay.
These are the steps I take in trying to master a class:
-Read the syllabus - Know what the teacher expects from the class, know the details of the class, know the resources the teacher recommends and look them up on Amazon reviews.
-Acquire my resources - Look up alternative books and websites I could use. Teachers sometimes recommend horrible overly dense books. Acquire the best possible resources that will work for you. Keep it limited. Ex: Teacher recommended a physiology book, way too much detail, would've taken me forever to read, especially since I'm a slow reader. I was recommended Costanzo - Physiology, read a chapter and loved it, that book got me a solid A in the class. Outside of your class notes, you have Wikipedia, and I think its a good idea to have at least 1 textbook that you would read.
-Plan out how to take notes - Does the teacher use power-point, does he write on the board, does he not give us his power-point presentation, do I want to use my iPad, pen and paper, do I want to go to class or podcast the lecture? All these questions can be answered within the first week of class. Usually I prefer FoxIt reader to annotate PDFs of the lectures on my computer in class. Some classes I prefer to listen to the teacher on podcast. These are all options for you to consider. But I think its important to listen to each lecture at least once. When they aren't reading off the slides, they give their own input and they are, after all, experts in their field. Much can be learned from their side-comments. I noticed when I prepare ahead of time, those side-comments tend to stick with me. When I go into class with no prior exposure, much of what the teacher says is in 1 ear and out the other, with no recall of him mentioning those things.
-Pre-Read - I briefly flip through the lectures for the upcoming week, then I read those topics in my textbook. I use Google/Wikipedia to clarify any questions. Then I read through the class-notes and compare what I just learned to what I need to know, and how that extra information helps fill in the gaps in the lecture slides. Pre-reading is the single best thing I've ever done in any class. You can't be a lazy bum about it. You have to prioritize getting it done. For example: Normally people study throughout the week and use the weekend to fill in the gaps and review what they learned. I used Sat and Sun to get ahead for the upcoming week, then I used Thur and Fri to review that week. I found this to be SO much more efficient.
-Frequent Quality Exposure - I think its good to aim for 5 exposures. My 6 were: 1) Pre-reading the textbook + Wiki 2)Reading class-notes 3) Paying attention in class 4) Reviewing at home on that day, comparing textbook with lecture 5) Reviewing thur/fri 6) Lab(Sometimes). I think equally important to exposure is the quality time you spend learning the thing. I treated each of my exposures as if they were my last and I would take the test the next day. When I pre-read the textbook, I told myself, I have to understand it now, there's no 2nd chance. By the time I even got to class, I pretty much knew everything. #3-6 were really just solidifying it. When you do that, you're able to be that guy who asks brilliant questions in class or that guy who sounds like he did research n this stuff, why does he know everything?!
-Practice Questions - From #4 and #5 in the above paragraph (reviewing at home), much of my reviewing would be doing practice questions. I cannot stress how helpful this really is. When you try to apply your knowledge you understand what you know and what you don't know. It really integrates your understanding with multiple topics. If you don't have practice questions, ask the teacher, or find a question book from Amazon.
-Personal Notes and Diagrams - Each time I sit down to study, I make a diagram or drawing of difficult concepts. I try to map out all the concepts to relate them to each other. This is essentially how I visualize it in my mind and its how I integrate my knowledge. I try to aim for 1 paper per lecture, I map out all the concepts, then I map out all the details. When I go back to study for midterms, or if I want to review the material in a future class, I just have to pull out my diagrams and it all comes back to me. Im super glad I started doing this early on in my education. I have so many diagrams, it keeps all my knowledge fresh. People wonder how I remember stuff in so much detail from so long ago, this is how. I'm a visual learner so this works for me. I don't usually do this until #2 when I'm reading through my class notes for the first time. The purpose is, everything I need to memorize, is mapped out on a piece of paper. It makes memorizing large amounts of information very easy.
-Research above and beyond - Once you know everything, take your knowledge above and beyond with Google, search professional journals, Wikipedia, you should be able to explain the topic for the layman to understand.
-Study for midterms very early - I try to aim to be ready for midterms 1 week before the test day. The last week is purely for review and group studying. I explain stuff to my peers and it really solidifies my understanding for long term.
Summary: The best piece of advice I can give is study to learn and understand. The 2nd best piece of advice I can give is, get ahead and build your foundation of knowledge very early in the class (I used a textbook to do this), that way any discussion, lecture, lab, homework, can all augment your knowledge. You don't be listening to the teacher like, "We don't have to know this." "Ehhh I'll look this up later." "What the heck, when did she teach that."
-Stay focused and study hard - Building "smarts" is much like working out. You cant walk into the weight room on your first day and bench 300 lbs, so don't expect to blaze through your material understanding everything. You might feel dumb at first, needing to read through very slowly just to understand it, and not getting it on your first try. Eventually you'll get so good that everything you learn sticks with you and automatically integrates with what you know.