About Post-Play Feedback Sessions: As a playwright, you have no doubt been involved in these. They can go well or they can go badly.
Usually when they go well, it is because you actively participate in the conversation, clarifying your intentions. Don't feel as if you have to answer questions, either from others inside the process/festival/conference (usually artistic advisors and/or the creative folks from other readings) or from audiences. And even though it's difficult to focus your thoughts after you've heard your play, try to consider what questions you want to ask the responders: Are you engaged from the very beginning? Did the ending make sense AND was it a surprise? How would you describe the play to a colleague? You can also learn a lot by asking which theatres might be most inclined to place the play in their season, because this question will place your play in the context of a community and an aesthetic. If the answer is Berkeley Rep, that tells you one thing. If it's Actors' Theatre of Louisville, that tells you something else.
The Liz Lerman guidelines, while a good start, can sometimes be so polite that you won't be able to derive what didn't work, what the obstacles were to engagement, etc. All the more reason to have your questions in mind at the get-go.
Who should moderate the discussion? Usually the dramaturg will moderate, but that is not always a good thing because if they have been working with you on the insides of the play for a week or so, they may have, if temporarily, lost their objectivity. At Sundance and at the O'Neill, the feedback sessions are moderated by the Artistic Director, which means the comments can stay focused on the text without necessarily being overwhelmingly "dramaturgical" in nature.
When your discussion is with a large group and/or audience, you may want the discussion to begin with a couple of advisories. I tend to start by asking the audience to not rewrite the play or to suggest scenes they'd like to see because the playwright wants to rewrite the play him/herself. I warn them that if they start to become prescriptive, I will interrupt them. I also suggest that questions to the playwright are most productive if they remain unanswered. These questions often, in the asking, identify a place in the script that needs your attention in one way or another. Questions can also be turned back to the audience for their response.
Finally, it's your process. If you have not had a chance to put in the revisions you know you want to do, you can decline the discussion entirely. If the institution needs to have a discussion with the audience as part of their community/marketing strategy, that doesn't mean you have to be there for it. At the Bay Area Playwrights Festival, when I was the A.D., I often led post-play discussions without identifying the playwright, who sat in the audience and wasn't put on the spot.