Off the top of my head:
-Cover the basics: be on time, don't duck out, be willing to take on and seek out responsibility, follow up on things without needing helicoptering from your supervising resident or attending.
*But make sure you know when to call in help. Never do something independently if you have not yet developed the skillset to do it safely.
-Get along well with others; be the kind of person they would want to take call with!
-Demonstrate competence. I will be asking myself, if I am your backup attending at 2 AM and you call me with an issue, how solidly can I trust your judgment?
-Work efficiently. If we have thirty minutes to complete an interview, show that you can do quality work within the set limits.
-Let passion for the field bleed through. Talk about your formulation of cases, about interesting topics that come up, and so on. Of course, read the situation and never let talkativeness get in the way of getting needed work done (see the first points!).
-Connect with patients, and show that you can foster a patient's attachment to you as a healthcare provider. Seeing you build rapport with a patient, and hearing positive feedback from patients about you, is a good sign!
-Show that you are teachable, that you are willing and able to fill gaps in your knowledge as you go along.