All of the above advice is great. As an interviewer and hiring manager here is some additional advice:
1) Demonstrate passion. This doesn't mean faking excitement and showing full-teeth smiles the whole time. Take questions and add personal context and demonstrate you have solutions to problems they haven't even thought of before.
2) Honesty and willingness to try are two critical behaviors. Realize there are different types of questions and different ways you should approach them.
a) Behavioral questions - "Give me an example of a time you and a coworker had a disagreement and the steps you took to resolve it". These questions need to be answered with REAL LIFE specific answers. Not "what I would do", but "what I have done". State facts, names, places, details. Take a minute after the question to think of the situation you want to present. Avoid just speaking right away and "creating" an answer. Lies or holes in the truth are easy to spot in these types of questions. Expect the interviewer to ask follow up questions on your details. These questions are often so generic it's typically unacceptable to say you don't have an example.
b) Technical / skill set questions. Realize that not all questions are intended to be answered and "knocked out of the park" by you. Often interviewers will ask questions they INTENTIONALLY DONT EXPECT YOU TO HAVE AN ANSWER FOR. They aren't testing you to see if you know it, they are testing to see how much bullshit you will spew as an employee. If you don't know the answer, simply state so. Often times that IS the correct answer. You'd be amazed how many people make answers up and attempt to pass it off as the truth. Believe me, it's as obvious as a little kid trying to lie to their mother/father.
b.1) Having said that, keep in mind that demonstrating how you would figure out the answer is key as well. If you don't know the answer, say so, but follow up with how you might try to find the answer. "I don't know, I haven't had any experience with that. But it does sound similar to XYZ that I do have experience with. I'd have to research it more, but if it is like XYZ, I'd try to do ABC. And if it isn't like XYZ I would try to figure it out by consulting my mentor, followed by reading a book, and finally asking you for guidance.
I could go on for days - but stick to what you know, be honest, demonstrate passion, and more importantly - be yourself. Good luck