Interviewing should be seen as a job in and of itself. It represents an opportunity for you to sell yourself and an opportunity for the employer to evaluate your qualifications, attitude, enthusiasm, analytical skills, communication and presentation skills and confidence.
Common sense is the most important thing you can bring to any interview. Interviews are, after all, a purposeful exchange between two parties with common interests. There is no substitute for good preparation and a conscious effort in preparing for interviews. However, your ability to "think on your feet" may well separate you from the crowd.