So to do well, consider the following:
0) GO TO CLASS, BUY THE BOOK, READ THE CHAPTERS, AND DO THE HOMEWORK!
1) Go to Professor's office hours early in the semester and Ask this question: "I know this is a really difficult class-- what are some of the common mistakes students make and how can I avoid them?"
2) If you have problems with the homework, go to Prof's office hours. If they have any "help sessions" or "study sessions" or "recitations" or any thing extra, go to them.
3) Form a study group with other kids in your dorm/class.
4) Don't do the minimum...for STEM classes do extra problems. You can buy books that just have problems for calculus or physics or whatever. Watch videos on line about the topic you are studying.
5) Go to the writing center if you need help with papers/math center for math problems (if they have them)
6) If things still are not going well, get a tutor.
7) Read this book: How to Become a Straight-A Student: The Unconventional Strategies Real College Students Use to Score High While Studying Less by Cal Newport. It helps you with things like time management and how to figure out what to write about for a paper, etc.
8) If you feel you need to withdraw from a class, talk to your advisor as to which one might be the best ...you may do better when you have less classes to focus on. But some classes may be pre-reqs and will mess your sequence of classes up.
9) For tests that you didn't do well on, can you evaluate what went wrong? Did you never read that topic? Did you not do the homework for it? Do you kind of remember it but forgot what to do? Then next time change the way you study...there may be a study skill center at your college.
10) How much time outside of class do you spend studying/doing homework? It is generally expected that for each hour in class, you spend 2-3 outside doing homework. Treat this like a full time job.
11) At first, don't spend too much time other things rather than school work. (sports, partying, rushing fraternities/sororities, video gaming etc etc)
12) If you run into any social/health/family troubles (you are sick, your parents are sick, someone died, broke up with boy/girlfriend, suddenly depressed/anxiety etcetc) then immediately go to the counseling center and talk to them. Talk to the dean of students about coordinating your classes...e.g. sometimes you can take a medical withdrawal. Or you could withdraw from a particular class to free up tim for the others. Sometimes you can take an incomplete if you are doing well and mostly finished the semester and suddenly get pneumonia/in a car accident (happened to me)...you can heal and take the final first thing the next semester. But talk to your adviser about that too.
13) At the beginning of the semester, read the syllabus for each class. It tells you what you will be doing and when tests/HW/papers are due. Put all of that in your calendar. The professor may remind you of things, but it is all there for you to see so take initiative and look at it.
14) Make sure you understand how to use your online class system...Login to it, read what there is for your classes, know how to upload assignments (if that is what the prof wants).
15) If you get an assignment...make sure to read the instructions and do all the tasks on the assignment. Look at the rubric and make sure you have covered everything.
16) If you are not sure what to do, go EARLY to the professors office hours...not the day before the assignment is due.
You might think that this is all completely obvious, but I have read many stories on this and other websites where people did not do the above and then are asking for help on academic appeal letters.