Like a lot of people have already said, everybody studies very differently but here is my go-to advice when anybody asked me about my 4.0.
1) Pick your classes and professors wisely (IF you can) - now, this isn't to say that you should pick easy professors or easy classes to get your easy way out. What i meant was using any rating web your school has for professors and pick those that are either well regarded by students or known to be good teacher of course. Talking to students who took the classes before you can also help you gage how good is the professor and how to approach the course. In term of picking the class, if its an elective course, try to pick something you are interested in because that automatically promote effective learning and likely better results. If you can't, go back to the "pick the better professors."
2) Talk to people! find out as much information as you can about the class, the professor's way of teaching/testing. This is not to say that you should go find out what is on the exams but more so what are the important concepts, how the tests are written, how did they feel about the class/professor, how much time they spent studying etc. Now again, everybody will give you slightly different answers but based on them, you should be able to articulate a strategy and study schedule.
3)Time Management (I don't think i need to stress this any further lol)
4) Practice: I think most schools have some form of a test bank where if the professors allow, old tests can be shared there as practice. Use them as practice (You are not cheating...it's good practice)! If old tests aren't available, talk to your professors about practices if required!
5) group study: if you decide to group study, always study by yourself first and spend your group study time on relearning from others, teaching others and resolving your confusion! Teach back method is notoriously known to help students internalize materials for long period of time (a lot of med school do this too)
6) Don't go on a tangent! Usually, professors will only test what they emphasize on class --> you should focus on the lectures or whatever materials the professors hand out! don't waste time exploring because you don't have that much time anyway. Create a solid foundation on what the professors emphasize is your goal! ( i usually only need the lectures + study questions if given and rarely any book materials)
7) Work hard at first.. play harder later (another poster already mentioned this) lol! It's super true!
8) Talk to your professor! Get comfortable to ask for clarification during office hours - This will help you get letter of rec anyway and your learning at the same time.
9) Don't forget your TA - They are your insiders! Talk to them, ask them what is the primary contents to learn in order to prepare for the tests, ask them questions etc. Get to know them! Network for your future courses - Many TAs teach multiple courses
10) Lastly, a 4.0, 3.9, 3.8 are essentially looked at equally in the eyes of ADCOM (anyone can correct me on this but this is based on my own experience). So don't freak out if you don't have a 4.0! 4.0 is a dime in a dozen anyway like Goro said!
Good luck studying 😀!!!! Hope this help!