Here's the BEST advice I ever got to answering these (or ANY) interview questions: practice, practice, practice!

This means, practice INTERVIEWING, not practice answering interview questions. Go to as many interviews as you can, even if you are not interested in the job (ESPECIALLY if you aren't interested in the job). The more practice you get with meeting new people and being interviewed; the better (relaxed, confident, and spontaneous) you'll be.

There are no right or wrong answers.... ok, there are some answers that are better than others. But the point of the interview is more about HOW you answer the questions, not the answers themselves.