The first time I did an in-person pitch I did all kinds of research on what to say and how to say it and how to present myself. We had five minutes for the pitch and I used every minute to blast that poor agent with every detail I could fit in. When I stopped talking, she looked shell shocked and was happy to pass me out the door.
The second time I participated in a pitch session, I had all the recommended info mentally in place, and the agent and I just had a pleasant conversation. I was prepared, but waited for her to ask me questions before I responded. I did not dump the elevator pitch, the full hook, the synopsis, motivations for MC, comparables, etc. in her lap all at once. We chatted. She gave me her card and asked for the ms. I was pitching the same book I had pitched the first time.
Bottom Line: There is a lot of good advice floating around, but there is also some questionable advice. Be prepared to discuss what your book is about - I mean really about - an elevator pitch, MC motivations, comparables, why someone would want to read your book, etc., but also trust your natural instincts on how to actually talk to the agent. Make the conversation as natural and friendly as possible. Smile. Thank the agent for his time.
In my first pitch I did not feel right about following the aggressive advice I had found online, but I did it anyway. I should have followed my instincts.
eta: I would just pitch one ms at a time.