Many professors don't grade exclusively from test results, but also factor in how much effort you put into their course. Professors have a lot to offer, not only in the classroom. Developing a personal relationship with your professors can be an invaluable resource for everything from letters of recommendation to career advice.
1. Make a good first impression—every day.
Come to class on time everyday, not only the first day. Punctuality shows that you care about more than good grades, but also about the class itself. Being late negatively impacts the way people unconsciously perceive you.
2. Don't skip class.
If you have to miss a class, try to let your professor know as far in advance as possible. Even in big lectures, professors notice when the room has fewer students than usual. Try to make up for work in advance. If a paper is due the day you will be absent, offer to turn in the class before. If you are genuinely very sick, you're probably still able to write your professor an email explaining the situation. Avoid any excuse other than the most straight forward. Chances are, your professor has heard them all before.
3. Ask questions.
Professors want to know if students are having trouble understanding something. That said, be sure to spend time with your reading and other study materials. Asking questions that your homework would have answered wastes your classmates' time.
4. Participate in class.
It is painfully awkward when a teacher asks a question and no one volunteers an answer. Speak up! You'll get more out of a class if you participate and stay intellectually engaged. It will also help to demonstrate to your professor that you are thinking about the content of the class.
5. Get help before you're in hot water.
Don't be afraid to approach your professor after class and talk to him or her one-on-one. If you're struggling in a class, the professor should want to help you. Ask them what he or she thinks you can do better. Most professors have open-office hours when you can come talk. Don't wait until the end of the semester, but address issues when you still have time to fix them.
6. Read the syllabus and follow assignments carefully.
A classmate of mine once turned in an eight-page paper comparing two pieces of Roman art, when the assignment was to look at two pieces of Renaissance art. It turns out, he hadn't even read the assignment. It's also important to pay attention to the details. Does the professor want your paper in MLA format? Did they ask for pagination? Professors get tired of seeing common mistakes.