Answer when they ask you questions/call on you, and not when they don't.
Ask questions at appropriate times.
You know that stuff 🙂
As a med student most places if you can even ID the site for the mystery slide in question, you're doing good.
Is there anyone there who already knows that you're interested in going into path? It might be worth a try to tell a friendly resident that you're interested in path as a career and ask their advice as to how to get the most out of your rotation, and who to target for a letter (I don't know what the work cycle is like or what you're observing in - presumably surg path? - but sometimes the resident can look at the sign-out schedule for you and see which student-friendly attending you will be most frequently on with; you can then work with that to try to get a good letter).