Go into the interview confident, but make sure that you do not act, speak, or behave as though you are entitled. Too many college students graduate with the idea that the world owes them their dream job, and employers are often repulsed with this attitude. Be confident, but leave it at that. Introduce yourself by name and be polite and thorough in answering any immediate questions. Save asking questions until you're asked if you have any.
Be respectful. The people interviewing you may be twice your age. They may also be not too much further along in their career with the company than you are, depending on the human resources policies and employment at a company. On a first interview with a major corporation, you may only be seeing the human resources interviewers. It's important to behave in a respectful manner to everybody you meet, even if you feel more on a peer to peer basis with someone.
When you're asked if you have any questions, be sure to have a few. You want to carefully prepare what questions you'll ask. Also, while you are listening to the interviewer speak, you want to be forming a couple of questions as well. This shows that you were carefully listening to what they had to say, as your question will reflect the attention you paid and the consideration given to his words. However, you don't want to seem as though you are grilling an interviewer. Be sure to ask three to five questions; then, thank the interviewer personally.