Tips for MMIs :
1) Don't panic. Its tempting to start talking as soon as you are asked the question, and to say the first thing that comes into your head.
2) Start with something like 'My first thoughts are ...' and this gives you a slight thinking pause, and then after stating a few ideas, say something like 'On the other hand...' or 'An alternative viewpoint might be that..' - this shows that you can think on your feet and are mature enough to see that there are opposing viewpoints, even if you don't agree with them.
3) Listen to any subsequent questions. You brain will be on overtime trying to work out if what you just said was sensible or not. Forget it, You cant change that bit. Listen to the next question and respond to what is being asked - not what you wish you'd actually said in answer to the initial question.
4) In the role-plays they are testing your communication skills - that isnt just talking, its about listening as well.
5) If its not clear what the question or task is - ask for clarification.
6) ALWAYS smile and say thank you when leaving a station - its all about showing professionalism.
GOOD LUCK!