Each site has their own expectations for Sub-Is so just follow what they tell you to do when you get there. Some sites want you in the OR almost 100% of the time, others want to see you in clinic as well as the OR. As for rounding on patients, that is also site dependent as to how they want you to participate in that. Some places just want you to just show up for team rounds others will assign you patients you will round on your own. In the OR you are expected to know information about the patients and the surgical procedures that you will be scrubbed in on. Most places will assign you a presentation to give at grand rounds sometime during the rotation. The presentation requirements are also site dependent, it could range from giving a simple talk on an interesting surgery you saw or a big in-depth presentation in front of the whole department that needs to be very professional/formal. You will also be required to show up to didactics every week.
As for shining on rotations aside from what has already been mentioned above. Here are the classics: arrive early, stay late, be on time for all meetings. Show interest even if it is not super exciting. Study up on the surgery cases and patient information. Find ways to be helpful (rotation dependent) as mentioned above, help the intern with starting notes, carry around supplies during rounds and gain the trust to change bandages, pull drains etc on your own (super helpful in keeping rounds going at a good pace). Rounding on the weekends is also site dependent, some places it is expected, some places it is a way to shine and some will say do not come in on weekends. Also if there are 3rd year medical students there, work with them and show them the ropes, your efforts won't go unnoticed. Personality is very important in Urology so make sure to hang out with the residents while at work and show up and have a good time at social get togethers outside of work.