If it still isn't clear, don't be afraid to say you don't understand what is being asked. These should relate to the employer, the interviewer, and the position for which you are applying. You can avoid painful silences by being prepared with questions and having done your research on the employer. Mention specific accomplishments that demonstrate your skills. If appropriate, talk about circumstances which might have contributed to a lower grade point in a given semester.
Personality is important.
Relax and try to convey confidence, sincerity, and maturity. Inject any relevant information about yourself that has not been covered, but which you feel is important to mention. If a potential employer has agreed to interview you, you have already impressed that employer with your credentials. You must then establish a personal rapport with the interviewer. Show some life and enthusiasm.