The interview is all about your presentation to your prospective employer. You want to appear relaxed, but attentive. BE ON TIME, there is nothing worse than having to apologize to the interviewer first thing, it starts you out in a big hole. Make sure you are dressed appropriately, you should be able to get the dress standards from your college placement office. In most environments, interview day is business dress, suits, etc. are usually the way to go. But check it out ahead of time.
When you are called by the interviewer, introduce yourself with a firm handshake and make eye contact right away. Make sure that you get their name, so that you can use it once or twice during the interview.
The interviewer is going to look for how you respond to a pressure situation, and what your people skills are like. They will most likely ask you some questions intended to throw you off a bit, in order to see how you respond.
This brings us to the emerging trend among employeers, which is the behavioral based interview. This type of interview is intended to give the interviewer a chance to see how you would behave under certain situations. Similar questions are asked of all interviewees so that the results can be objectively compared from person to person. From this perspective, this type of interview is more fair to all involved. The behavioral based questions are not 'yes' or 'no' questions, but intended to elicit a detailed response. The questions are also set up so the a good interviewer can follow up with more detailed questions if you don't provide enough of an answer.
A few examples of behavioral based questions are:
"What do you consider to big your biggest success in the last year?"
"Have you ever participated in a team situation, either as a leader or a team member, and if so, what were your experiences? How did you work with the different people on the team?"
"Have you ever worked on a failing project and what were the reasons that it was in trouble? What did you do to help turn it around?"
"What has been your most challenging course or project and what did you do to meet the challenge?"
"Suppose you were a team leader and one of the people on the team was not doing their part. What are the steps you would use to handle this situation?"
"If you found out about a co-worker who was doing something illegal or unethical on the job, but you had not observed this behavior firsthand, how would you handle this situation?"
As you can see, these types of questions don't usually have any 'standard' answer. It is ok to have a short pause before you answer, to show that you are thinking seriously about the situation, but don't take too long. Give as thorough of an answer as you can, or the interviewer will almost surely hit you with a followup question to draw you out more.
One way to prepare for this type of interview is to hold mock interviews with your classmates and evaluate each other on the response. It will give you a sense of being in 'the hot seat' and will lead to your comfort level at the actual event. However, if you get a question that you have practiced for, don't rattle off the answer as if from memory.