Everyone there has a common interest. Never whine, gossip or speak badly of a fellow artist or employer. Be nice to everyone. It's a small world, especially in the entertainment industry. Prepare for meetings by reading the trade journals or the program.
Dimension usually prints a bio of the speakers who do the presentations.
These bios and the program is on the web site before the meeting. Read those bios before you attend the meeting. Find out about the people you are going to meet. Do your homework. It ll be easier to speak to people if you know something about them.