If it is possible structure your answer so your interviewer has a clear understanding of your thought process, e.g., "there are three common problems in the conversion of UNIX files to the format that would be compatible with this type of GIS system."
Make sure to expand on your answers, e.g., do not say I did Java programming over summer. Go into some detail about the project and make it relevant to the job at hand. Often, students give very sketchy responses to the questions.
Most interviewers often ask at the end "Do you have any questions for us?". This is a good opportunity for you to highlight knowledge you have on the issue, on the company's past work, or skills that you did not mention in the interview, e.g., "I understand that last year your firm developed a program that Did you have this problem in coding this program? I know that Y companies developing a similar program had coding problems because ... How did you deal with it?". Please note, however, that if your interviewer is a Human Resources representative they may not be able to answer these types of questions.
After the interview do not contact the firm directly, your co-op coordinator will do so on your behalf. You may consider sending them a thank you letter that reiterates your interest in the job but always consult your Co-op Coordinator before doing so. E. Questions to Ask the Interviewer.
Do not ask a question you think the interviewer can't answer. Never embarass the interviewer!