Go to every class, pay attention, take notes and read the assigned material before the instructor lectures on it. Going to every class will force some of the material into your brain even if it's just by osmosis. It will save you studying time later.
Buy several packs of 3 x 5 note cards and use them to memorize the nomenclature. Memorizing the nomenclature is key because a) memorizing is time consuming but easy, and b) if you don't, you'll have no idea what the lecture was about, and if you fall behind, you probably won't be able to catch up until next semester when you have to repeat the course.
Form study groups with people in your lab. It's easier to make friends in lab because the atmosphere is more relaxed and you can talk to your neighbor and commiserate about the instructor.
Explain the concepts you think you understand to someone who has never heard of organic chemistry. Use simple terms and do it in your own words. If the other person gets the concept, it means that you're learning.
Get copies of old exams, preferably ones given by your instructor. Be sure that you can answer all of the questions.
Cram if you must, but promise yourself that next time you won't procrastinate. Practice your flash cards on your way to the exam, but don't get hung up on anything you don't know.
Relax during the exam. Nothing will undermine your confidence as much as panicking over a few questions you don't know right off the bat. Skip the ones you have trouble with for a bit and finish the ones you know first.