Congratulations on landing an ICU preceptorship!
Arrive on the unit early and find out who your preceptor will be. When she/he comes on the unit, introduce yourself with a friendly smile. Preceptors can be shy, too, and it's rather intimidating to walk on the unit and see five or six students standing around and not know which one (if any) is yours. Ask someone who doesn't appear busy (always a crapshoot, I know) where to put your purse, hang your jacket and go to the bathroom.
You may not know who your assignment will be before your preceptor arrives, but if you do, and if there's a free computer (please don't get in anyone's way who is trying to finish up charting and go home) look up your patient's history, meds, etc.
Arrive on the unit with a list of objectives. I'm sure your school provided you with such a list. Compare the objectives with your patient assignment, so that when the preceptor asks what you need to work on, you can tell her. Also, be sure you know what you can and cannot do. Some students can give medications, others cannot. Some can give PO meds but not IV, etc. Some can start IVs, hang IVs, etc. Know what you can and cannot do; don't depend upon your preceptor to know. We get students from several schools, and they're all different.
Ask questions about anything you don't understand, but try to ask them in a thoughtful (not pestering) way. Understand that the patient comes first, and if they're trying to die the preceptor is going to be trying to prevent them from dying and not teaching you.
Learn to take criticism gracefully, even if it is less than gracefully delivered. Even if you're sure it isn't valid. (And even if you're sure it isn't valid, take some time to think about it very carefully anyway because you may find that it IS valid. And you might learn something.) Ask for specific feedback. "You did a good job" is great to hear, but what you really need to know is WHAT specifically you did great and what you need to improve.
Please don't take things personally; develop a thick skin. When I was a new nurse, my preceptor walked around the last few hours of our shift with a frozen smile and a brittle laugh. I was sure I had done something wrong, that she hated me, that I was the worst nurse in the history of the unit. (Well, I probably WAS the worst nurse, but I digress.) It had nothing to do with me; her husband had been in an accident and she was just trying to get through the shift so she could go to the ER to be with him. Years later, I realized that I had just put a student through the same trauma the shift that I got the news that my father had had a heart attack 2000 miles away, and someone had to come and take care of my mother because she was driving in circles around town and couldn't figure out how to stop the car.
Your patient will have a diagnosis, medications, labs and tests. Look them up and know what they are and what they mean.
Sometime during the semester, bring treats for the staff. It isn't necessary and we don't expect it, but when students DO it, they really stand out in a good way! I'm sure there's more, and I'm looking forward to seeing what other people post. Good luck.