As an academic advisor, I want to encourage you to have a holistic approach to your college success. Improve your study skills is the most direct answer: a tool to do that is https://www.coursera.org/learn/learning-how-to-learn - a free online course that will take about 9 hours to complete. You need to take good care of yourself and your brain for you to be able to excel - good nutrition, regular exercise and good sleep habits are essential. A good book that you can use as a manual for success in college and beyond is Adam Burke's Learning Life. Here is a review on it that I wrote: https://www.nacada.ksu.edu/Resources/Book-Reviews/Current-Past-Book-Reviews/Learning-Life-The-Path-to-Academic-Success-and-Personal-Happiness-Review-by-Anna-Traykova-Kennesaw-State-University.aspx
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Great question, and the fact you are even asking it shows your commitment, so good for you!
I see you've received some great advice from Anna already.
I'm not an education professional, but I can offer insight as someone who went through not only undergrad but also graduate school committed to getting the very best grades I could.
In my experience, it all boils down to effort - you get out of it what you put into it. It sounds boring and obvious, but there is no magic formula. Hard work and dedication will almost always be recognized and appreciated by your professors - they love to teach people who love to learn.
That said, here are a few tips for you:
1. Don't procrastinate.
Some classes may be harder for you than others, and will require more time. You may be tempted to push that classwork off to the side to focus on other classes or assignments that are easy for you. Don't do it! If you have a tough class, focus on that work early in your study time, so you can approach it when you're fresh.
2. If you need help - Ask!
If you struggle to understand a topic, meet with your professor during office hours to go over the material. (Tip - it's much better to do this in person than over email.) When you meet with them, show them that you've at least tried to understand the material - for example saying "I'm having a hard time understanding the differences between three types of horizontal gene transfer - can you step me through them?" will be much more productive than just saying "I don't understand this chapter on genetics. It's too hard!"
Also, don't be afraid to ask other students for help - in one of my college chemistry classes, there was this girl who was super-smart and always got the highest grades (I know that because our prof always posted all of our grades outside the classroom door after ever test and quiz. Humbling, but useful.) I always sat next to that girl during labs and group tutoring. I learned almost as much from her as I did from the professor!
3. Treat college like a job
If you take college seriously and use it as the gift of wisdom and learning that it is, you'll get the most out of it.
It's important to have friends and to enjoy the social aspects of college, but don't take it too far; resist the urge to attend parties in the middle of the week, don't blow off studying in order to just hang with friends, and don't make the mistake of staying up all night and thinking you can attend a full day of classes the next day! Take your studies seriously, treat your professors and instructors with respect, and you'll go far.
4. Don't overload your schedule
I made this mistake several times in undergrad. I once took 7 classes in one semester and nearly burned myself out physically and mentally in the process. Work with your advisors to make sure your course load is balanced and reasonable. And (unlike me) listen to them if they tell you your course load is too heavy!
5. Volunteer for extra credit
This is somewhat related to the above point (if your course load is too heavy, you won't have time for extra credit opportunities). When I was a student, I always asked my profs at the beginning of every semester if extra credit opportunities would be available.
If I liked the class, I enjoyed the extra work, and if I struggled in the class, the extra credit always helped with my final grade. Once, my extra credit work even bumped my final grade from a B+ to an A! So I can tell you from personal experience it's worth it.
Those are my top 5 tips for you. Beyond that I can only say, enjoy the experience, be kind to yourself and others, and have a great college career!