[Retroman]

In my opinion, over preparing your answers to questions can often make you even more nervous...
Especially if a question comes up that you didn't prepare for. And you even find yourself a little nervous trying to remember the exact answer you came up with in your head the day before, instead of just talking naturally.

My advice is to write down some questions yourself, then get a friend/family member to think of some random questions you'd never thought of...
Then get them to read them out in random order and practise coming up with instantly good answers to all of them on the spot =]

That way you're prepared for anything, as your ability to answer questions quickly and efficiently will improve and it won't matter what they ask you.

My last interview was a group interview, so it was a lot less formal. Which luckily meant getting to make new friends and took the pressure off having to answer questions.

But yea, besides that it's just the obvious really...
Try to smile, be polite, ask some good questions if you can think of any, talk clearly. And just realise that they're people too, and they're also having a conversation with a complete stranger, so as long as your social skills are decent it shouldn't be a worry.

Make them feel at ease with you, as much as you're hoping they'll make you feel at ease with them =]