You can expect a little less of the behavioral-style questions at this part of the interview. They will try to be more specific about your chemistry and cGMP procedure knowledge, and look to see your personality shine through. Try to relax as much as possible, so you don't come of as a "dead fish", if you're ready to answer more of the same questions that you already answered, you'll be calmer, and you'll be able to project your personality without obviously looking "phony"
Think to yourself: what can you do based on your previous lab experience? Analytical instruments don't work like Star Terk tricorders -- our instruments generate the correct answer only when setup properly, with the correct solutions (HPLC eluent, analytical standard solutions, etc.) properly prepared and the system properly conditioned for use. Did you do something similar in school? Preparing buffer solutions correctly, setting up an organic synthesis rig properly, etc. try to be able to talk about that. What can go wrong, what did you do wrong, and how did learn to do it better next time.
What else did you do in school. The group leader and validation supervisors will care more about your ability to write clearly, maintain a personal organization of the tasks before you (executing them in a timely fashion, not forgetting important steps, etc.) Does that describe something you've done in other classes in school, or even your hobbies or other interests? See if you can spin the conversation that way.
I was only taken out to dinner once, and I was a little nervous. I tried to be personable, polite, talk about interesting things (so I didn't look like a dead-fish) but still let the interviewer have control. I didn't get the job, and I worried if I had done something wrong. Many people told me that dinner and lunch are just formalities, the company budgeted for the cost, and is simply spending their budget. Perhaps the only thing that interests your interviewer in this situation is a free meal for himself at company cost -- or perhaps not.
Look at this:
http://www.capandcompass.com/ This is a company that produces a little book I saw at my local library. It addresses some of the questions people face when they first leave college and start the working world. On some level its even more simple than the many "for Dummies" books. But on another level, its useful for a complete noob, so you can see what information you have to read up on. I wish I'd had some of this information when I was a recent grad. They talk about company dinners in a funny sort of way.