It will probably all depend on the surgeon, the case, and the how things are going. I think it is fine if you ask questions, just as long as you are not pestering. If the surgeon seems happy answering you questions then keep on asking. If they give you short, curt answers or if you feel the tension in the room rise then perhaps it's a good time to lie low and just observe. If you are not scrubbed in you can often chat with the anesthetist (they can tell you a lot about whats going on)...just keep your voice low so as not to disturb the surgeon.
If you know what cases you'll be in on then read up on the anatomy of the region and something about the procedure. If you are scrubbing in, the best advice is just be sure you scrub longer than anyone else. If you are retracting, don't get a lazy arm. If they ask you to do anything (ie., put a cather in, assist in cutting, cutting the sutures, etc.) and you feel somewhat comfortable, then accept the offer and try it...otherwise they might not offer again.
Have fun...
