I have realized my ways of studying suck, how do you study?
Don’t just cram the day before. However, it happens; if you’re studying unproductively late one night, just go to sleep. Can’t stress that enough. Additionally, ask your teachers your questions and for help if necessary. Good luck!
Take notes on everything in class (if you don’t know how to take good notes quickly, learn - there’s a ton of methods online to try); it doesn’t matter in what format. Then, in the days leading up to the test, go through your class notes along with the textbook, and rewrite them in a designated notebook, adding info from the textbook where necessary if the teacher didn’t go over it in detail. Writing things down refreshes them in your mind, and having one small notebook with all your notes is great for finals (or if you ever need the notes in another class.)
Of course, what works for one person doesn’t work for everyone, especially considering that there are different learning styles. Seconding the advice of @mak902. Try a bunch of different methods and find one that works for you.