1. Take advantage of your professor's office hours- All professors have a designated office hours where they are available to answer questions and help you understand the class materials if necessary. I've met up with several of my professors for my harder classes, and they have always been helpful.
2. Read ahead for class- Reading ahead for class really helps. Personally, it helps me try to understand the material before the professor lectures about it in class, and I can also get questions together for class incase I didn't understand specific concepts.
3. Find a study buddy- I was having a hard time understanding the material for my psychology stats class, and just reading the material for class and trying to understand it by myself did not help. When I found another student who wanted to study outside of class together, it was easier for us to focus and help each other out with concepts we didn't understand.
4. Write notes in class- Listening and reading concepts for class helps to a certain degree, but when you write notes, it helps you remember the material even better. Have a notebook for each class so that you can use your notes to study for quizzes and exams when you need to do so!
These things have helped me over the last two years. I hope this is helpful for you too!