been thru the interview a couple of years ago already so heres my take on it:
1. go FORMAL!! yes good impressions count for lots at interviews!
2. SMU interviewers will not ask the tell me about yourself questions. it'll likely be a panel interview so do make yourself stand out from the rest of the others being interviewed at the same time with you.
knowledge of current affairs will be good so you can insert relevant examples to prove your point
3. for business school: Marketing is evil. debate.
for law school: what do you think about IRs? what do you think about organ trading?
4. I think they look out for: confident people, people who arent afraid to offer (and substantiate) what THEY think about things (even though it might be different from what the rest of the other interviewees think) and people who are able to speak well and present a well informed, professional image overall
5. max half and hour but there might be an essay session following the oral interviews