I had a creative way of preparing... it's kind of funny.
An anti-abortion group came to school and I decided to just discuss the issue with them. I'm not talking yelling and screaming "YOU SUCK," either. I mean honestly getting at what they think, what I think, and respecting each other and what we believe.
Honesty I learned a lot about it and now I understand some of the reasons people feel that way, though I don't.
My point is being able to approach a situation like that where it might be tempting to get emotional about it was healthy. They asked me some tough questions, I responded with more tough questions.
Just learn to be confident and up-front with what you believe and think, and don't be forceful with it. Some people come into interviews acting like they own the place, and that's almost as bad as being nervous or shy.
Whatever your political beliefs, I look at Barack Obama as a great example of how to interview. Look at your interviewer and just tell it like it is. Use your hands because it shows you are engaged in the conversation and helps you punctuate without raising your voice or using strong words.
...so on. It's an art and you may hate/love the guy, but he won.
That's largely because of being prepared and engaged in conversation.