Some of this will be repeats of what's already been said above, but I'll share anyway.
We do group interviews at my current organization. I was on a few panels. We did a whole round recently for an open position. Some did well, and some didn't. Things I noticed from those who did well:
-They knew about the organization.
-They made eye contact with everyone and didn't appear nervous (or, as nervous)
-They took notes and asked probing feedback questions.
-As the names of the panel members were disclosed beforehand, candidates had an opportunity to look us up on linkedin. Those who did well did that, and knew when to use what they found without sounding like stalkers.
From those who didn't do well:
-They were visibly nervous or intimidated.
-They didn't listen or take notes and weren't able to adequately answer our questions.
-They didn't know anything about the position or the org. Responding to "what do you know about (org)?" with "ummm, its an airport?" is not a good start. Even if it is an airport.