Attend every class. Even if there are circumstances that cause you to be less 100% attentive, you should still attend.
Not all topics are equally important - part of the learning process is to organize the course material in your own mind so that you can use it most efficiently.
Expect to work for long periods of time on hard problems, so look for a quiet place where you can concentrate. Mix up working alone and with others. One the most effective ways to study is in "study groups" of three to four students. Some instructors will actively organize these groups, while others will just encourage them. Just as with the class, attend all study group sessions - you will shortchange yourself and the others in the group if you are absent from a session.
Find someone to teach. You've really learned something when you can explain it to someone. This is why I strongly encourage you to work in groups and to discuss the material outside of class.
Be critical of what your write. You will be expected to write out your assignments and exams in coherent sentences. So when you do homework do the same.
Estimate solutions. If the solution to a problem is going to be a number, take the time to estimate the solution beforehand. Even a very rough estimate can help you avoid making a mistake and reporting an answer that is obviously wrong.
If you don't understand something, ask!
Don't neglect your other classes. Budget your time. I wouldn't advise that you carry your calculus book around everywhere, but you should always carry some paper and a few problems (either in your head or on paper) that you can work on when you have some spare time. You can even think about some problems while you drive or run or swim.
Take notes, but not at the expense of listening. Here are some ideas for note-taking:
Tutors: Calculus Tutors and Teaching Assistants are available at the the North Campus Centers for Learning tutoring center. Schedules are available at the Centers for Learning. Tutors can be useful, but they can also be misused. Don't expect a tutor to learn calculus for you. They can help you learn by guiding you through the thought process involved in a problem, or clarifying a concept. But if you simply ask your tutor to show you a solution to a problem you are unlikely to learn much from the experience. If you are stuck on a problem, ask your tutor for a hint. A good tutor should be able to give you just enough information so that you can do most of the problem-solving.