Keep in mind that, at every institution, surgery is SOMEONE's first rotation. Be sure to contact whomever before your rotation starts to find out where you should be, etc... Get the surgery schedule and know what cases you'll be going in on. Find out who your resident is and just let them know you'll be starting. I also recommend the Wash manual surgery survival guide. It tells you all about the lines, drains, tubes...etc...you'll see on surgery that may intimidate you. It also goes into how to deal with the surgical patient with regards to diarrhea, nutrition, constipation, pain... I have found it to be very valuable and NOT just surgery related. See if one of your classmates have it and borrow it, as it isn't something to carry...it's just nice to know about all those lines and stuff you'll see when you go in and see a patient.
My other thing (and - keep in mind-I am going into surgery, so I absolutely love this stuff!) is to ask "WHY?". Not in a challenging manner - as if you know a better way to do the procedure......but in a genuine inquisitive manner. For example, if you read on a case and you read that the procedure is done one way, but the doc is doing it another way - just ask why he is choosing to do it that particular way. Tell him/her what you read and ask what the difference is. That always helps me remember things better. Or, if you are thinking one antibiotic, but the resident writes for another - ask why.
Now, about questions...you need to get the feel/atmosphere of your rotation before you go about asking things. If the OR is silent and your doc doesn't talk...mmmm....maybe you better not say anything. However, to avoid any mistakes - I simply ask the residents, scrub nurses, or the doc himself if it's okay to ask questions during the procedures. The nurses are wonderful when it comes to things like that. I always ask "what do I need to know when doing a procedure with Dr. so and so??" They are really good about letting you know the little quirks an attending has.
Also - when the procedure is over - you don't leave the room! (unless it was a long one and you need to pee...but come back) You need to stay and help move the patient. Or, if the patient was only under sedation - you stay around and ask the nurses if you can help. They may say no, but it's always appreciated. Also, when the patient comes into the OR - you need to put the foley in (make sure you are the one responsible for this in your OR - ask your resident/attending). Let the nurse know that you'd like to try, but need some help.
Another thing I've found is that sometimes the docs need the CT films or whatever in the room with them. I make sure they are there. Usually they are already sent for by the nursing staff - but a couple of times, I actually had to run down and get them because they were too busy.
Be nice, be helpful - but also stay out of the way. Ask the doc/res if it's okay to check on post op patients on your own. Most don't mind, and encourage it - but I had one who only wanted me there for procedures and didn't want students contacting his patients otherwise.
Know your knots if you want to suture. The OR usually has left-over opened suture they will let you have to practice (at least our does). You can practice tying knots all day, but when you actually get in there and you have gloves on and you are holding the needle driver - your fingers don't know what to do - so practice the whole sha-bang.
I think that's all. I know others on here post about how bad their surgery rotations are....and that's too bad. I had wonderful experiences. Hopefully you will too.