Done 2 in my time, got through both.. no experience of the SIA one though, but some generic stuff I can give for sure.
Good advice above... to which I'd add be a social animal, move around, talk to people. If you do have a beer, please don't have too many.
Avoid controversial topics that cross boundaries; politics and religion being the two big ones, simply because you cannot guage the person you are speaking to.
Also, be very aware of the culture of the person you are speaking to.. Lee has given you an Asian perspective on that, may I add a complementary Western one; if you are talking to an Australian, please do not go cracking jokes about Australian foreplay consisting of "Brace yourself, Shelia!" or similar. Believe me, it happens.. person I am quoting directly there did not get the job. Funnily enough...
Similar applies to all cultures and countries....
Good luck. Best advice is simply to be yourself.. trite though it sounds, it will show, believe me.
£6