OK, first there's a few things that are really important, for any interview but it seems i found these types of questions more in Texas interviews (hit them more often and they seemed to be the really well emphasized question).
Firstly- why medicine? This one is a lot tougher than i though. I remember showing up to my first interview at UTH and this was the first question out of the first interviewers mouth. You do NOT want to be like me and ramble on for 10 minutes about some EMT stuff, how you liked bio 112 and how your appendix ruptured when you were 5. You want a succinct, not trite, unique answer. "To help people" is a no no. Hear it from 4 people and you'll know why. THink of something true but that's not something everyone would say. By the end of my interviewing i had a nice answer that included interactions, working with hands, relationships, etc.
2nd- why here? You have to make it something about the school. So at the TMC don't say "because of the TMC" only, because that goes for Baylor and UTH, which are both very different in their styles of teaching medicine. Read some viewbooks, talk to some students BEFORE the interviews (student hosting is a great way to get this inside info) and give them a realistic response that shows you've cared to get some info on the school. An open ended response that could apply to any school in the country will do you no good.
3rd- ethics. I only got these questions at my texas interviews. Fluke or standard procedure i don't know, but you have to be prepared. When my UTH interviewer came out with the "who would you give the kidney to out of these people?" (insert 8 people including family, president, etc)- i ate it bad as i paniced. A bit of prep will help you, but most importantly, STICK TO YOUR GUNS. I later learned this from another interviewer- they just want to see you make a decision and defend it. Of course, i picked one and as he laid into me about the others, i went through all the choices. Not good, but i had no clue. Read up some on ethical questions, the latest biomed advances and their associated ethics and so on. It seemed like last year we were in the midst of the stem cell debate so that was on everyone's mind. That seems to have been relegated to a back seat now, so i wouldn't worry about the mechanics of this stuff- just have an opinion and back it up. It's important to have a spine and no one will hold it against you if you have an opposing viewpoint to theirs, but have thought it through.
That's about most of the texas-specific things i saw on the interview trail (of course ther'es a lot more, but a quick interview search will yield all that). Most important, be honest and be calm. If you like medicine because of the fact you're guaranteed a 200K income, say it. It won't be held against you cos most doctors are glad about that too. Also, if you are getting really railed, just stay calm. Don't say "i dunno" or "who knows" or something if you're exasperated. Take some time and think. I had an interview at UTH where the guy was really working me, and i did get really edgy and worked up. Don't be like me!
After a few interviews it'll be old had and you'll be telling the same stories over and over. Just make 'em sound sincere and you'll be good to go. --Trek