lynx,
Seriously, and I know this is said all the time, just be yourself. I went for the "getting to know them on a more personal, less formal" note and it must have worked. I tried to make them laugh while laughing with them, if you have a good joke or are just naturally funny, use it to your advantage. All the adcoms want from you is a reason to let you in to their college, not a reason to keep you out. Be yourself, dont front on ficticious stuff and be true to yourself and to them. Do you, and do it well.
Best of luck to you.