How do I best prepare, as someone who is quite introverted and unaccustomed to this intense form of socializing? I will be practicing questions, but what else? I want to knock this out of the park.
Take a notebook to make notes during the interview. Make a TODO list for your own questions, things you'd like to know about the company and the team. Update the list during the interview every time something interesting shows up; you can go back to this thing and ask about it.
You can also prepare a set of answers for those unrelated and/or unnecessary questions like "what was your worst conflict in the career" or "what's your weakest point", especially if you have a list of the ones you hate. Note that it's more important to have prepared the list than to have it.
On a similar note, list your own projects and tasks you were most proud of or that were especially challenging. It's a handy thing to have in case your mind suddenly goes blank.