1. Make a point out of studying at least 15 minutes each night. Review what was done in class. Then you won't have a mountain of work on the day before your test and you can impress your teacher every day.
2. Look at the teacher's eyes when he or she is talking. Studies have shown that the student who looks the most attentive is the one the teacher thinks of as the good student. This takes care of the subjective part of every grade. The side benefit is that you do learn more when you are focused.
3. Save your social life for after class. It will be all the sweeter.