Agreed that the number one rule is to not be annoying.
For bonus points: Be engaged, find a research project, do a presentation on an interesting case, and network.
Try to get access to the EMR by the first day and bring your laptop so that you can be reading about the patients and looking at the images on your laptop. It can be hard to stay engaged while watching someone read, so challenge yourself to read the image alongside the resident and come up with impressions and questions. If the department gives you the opportunity to give a presentation (I've had one rotation where it was required and another where it was optional), pick something interesting and give a great presentation. If you meet any approachable faculty early in your first week, ask them if there are any research projects they need help with (set expectations based on the amount of time you have in the rotation and your experience with research - do not offer anything that you won't be able to follow through on).
As far as brushing up beforehand, review the basics of the modalities used in that specialty. Be able to answer easy questions, like, how do you differentiate a T1 image from a T2. For resources while you're looking at cases, you can use headneckbrainspine.com for neurorads or radiologyassistant.nl for anything else.
And lastly, use your away rotation as an opportunity to network. Find out if any of the residents came from your med school and email them the first week, asking to go to coffee or something. Ask the residents that you know at your home program if they know anyone at your away. Meet with any connections and learn more about the program. If they see you're interested and they really like you, they may set you up with someone important from the selection committee. If you don't have any connections, try to set up a meeting with the program director anyway to find out more about the program.
Also, in general, don't be uptight. Radiologists are a fairly laid-back group. I was doing an away rotation in one department, but I met residents who invited me to come join them in a different department for a day at a time. I just asked the coordinator if that was cool, and everyone was fine with it. Use this time to get the most out of it- if the program has different sites, ask if you can go to a different site for the day. I think you are more memorable when you act like an adult who is trying to get the most out of the experience.
