not-live-blogged about this meeting here.
The first is laying down the ground rules. Program chairs tend to assume that PC members know basic things like not to leak information during the PC meeting (emailing your students or colleagues when the paper is being discussed), not to express an opinion on papers you didn't review, and not to compare the paper to the version that was rejected last year. This stuff seems obvious but it's amazing how often people forget.
The order in which papers are discussed is another important decision. In this case there is no one-size-fits-all model. In my opinion, the best model is to group papers by broad topic areas, and within each area discuss the best and worst papers in the group first, followed by those in the middle of the group. This helps to calibrate things and keeps the discussion focused on a set of papers with some commonality. The worst model, I think, is to discuss papers by order of submission number (which is effectively random), since people don't get calibrated that way.
Keeping the discussion to a time limit is very important. Many PC members think that it's their job to hold forth about every minute detail of the paper during the meeting. Once, there was a case where the lead discussant went on for about 6 minutes about a paper, and when finally cut off and asked what he thought the decision should be, said "I don't care!" PC members need to remember that the audience for this discussion is the chairs and the other reviewers (the other PC members are usually reading email or otherwise ignoring discussion of papers they didn't read). So keep it short and sweet, and respect everyone's time.
Dealing with conflicts is always a huge pain. It is disruptive to ask people to leave the room and then call them back in later. It would be awesome if HotCRP could automate this (coming up with a paper discussion schedule to minimize the number of times someone has to leave the room). I'd like an iPhone app that automatically buzzes people when they should leave and come back into the room -- a lot of time is wasted in PC meetings with these context switches.
It has to be recognized that reaching consensus is not always possible. PC members have to accept that they will win some and lose some. I dislike it when the discussion comes down to a vote amongst the reviewers, since that is rarely a good way to decide these things, but at least it is quick and painless.
The last issue is the role of shepherding. This should be explained clearly by the PC chairs at the start of the meeting. Personally, I am in favor of shepherding every paper for a major conference, with the goal being to ensure that the final paper really satisfies the reviewers' main comments and the writing is cleaned up (as it often needs to be). In general, shepherding should not be used to get the authors to run new experiments or change something technical in the design -- it should be limited to changes in wording or positioning of the work. This question comes up at every PC meeting I've been on and setting expectations early would make things easier.
Check out my related post on the psychology of program committees for a behind-the-scenes look at what happens behind the closed doors.