An interview is a two-way process: keep in mind that you seek a job that meets most of your interests and requirements, allows for growth, and provides the environment in which you will be productive.
Through an interview or several interviews, you will be able to assess whether a job or a company fits your criteria.
You and the interviewer each have a need: you want a job and the interviewer wants to find the right person to fill the position. The initial interview, whether on campus or at the company's location, is usually an opportunity for screening. The interviewer forms an impression of whether your qualifications, personality, poise, ability to communicate, and general "fit" with the organization make it worthwhile to continue the process.
In addition to the specific job-related skills and knowledge you possess, the interviewer is interested in your motivation and whether your interest in a particular job is based on realistic knowledge of its content. The interviewer also wants to know what you have done, how you value your accomplishments, and how you relate these experiences to your career interests.