In short, just be yourself (but the "self" that you are to acquaintances and strangers, not the "self" that you are to say your old college buddy). In other words, be on your best behavior, but it's not about impressing your host.
In other words, the only way word could ever get back to an adcom is if you were a complete jackass, or acted like Borat.
As or discussing strategy/profile - if it's a very casual thing, sure, but you have to be the judge of that; if they ask about your b-school plans and offer up the opportunity for you to ask them, sure. But if they don't, you can look like a doofus (you might as well silkscreen "700 GMAT/3.4GPA/4 yr WE/[nationality]" on your t-shirt and complete the package of being a complete dork.
Again, just be yourself - you are the guest, doing the inquiring. When it comes to school visits, it's about you evaluating the school (and when it comes to the actual admissions process, it's the other way around).
May I ask which school you're visiting?
Alex Chu
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com