Show up to class. This seems ridiculously fundamental, but each class missed is a significant segment of the course. And students often can get disoriented when they miss a step in the sequence. So go to class. Every class.
Sit in the front, as close as you can to the teacher. It's easy to get distracted in the back of the room. Maybe you can't hear exactly what's being said. Maybe you are spacing out, staring out the windows. Maybe you are focused on trying to read the back of a baseball cap. Nothing positive comes, in terms of learning, by taking a back seat.
Listen carefully. Teachers generally talk about every single thing that will be on a test. They typically aren't trying to sneak things by you. So if you listen carefully to what they are saying, you probably have all of the answers for the test already.
Ask questions. Lots of questions. If you don't understand something, it could be the step that puts you in a tailspin. You are paying for this education, it's your right and obligation to get what you can from it. Ask about things that are unclear. If you don't want to do it in front of classmates, make a note and then ask the teacher after class or during office hours.
Keep up on your readings. Do a little bit every day. Understand it. Review other parts and how they fit in, and then keep it fresh by taking additional notes on what you've learned and what questions you have about the readings. Don't wait until the day or week before the test to try to cram all of it in. Your brain just can't absorb that much information in that short of a time.
Compare lecture notes with reading materials. The more crossover you see, the more likely the material will be on the test.
Talk to your teacher. Get to know that person, who will be giving you your grade.
After a test, look over all of the answers you missed, and try to figure out why it happened. Where were the holes in your studies? Where did the questions come from, lecture or reading materials? What were the other clues in the crafting of the questions? If you don't understand why you missed a question, ask your teacher.