Hour interview, that's always fun. The tips I'm giving is assuming this is a decent size company.
Did they mention how many people will be interviewing you? That's always good to know. I'm used to typically two people.
If it's an HR person than don't expect a technical interview. It also won't be a great interview either. HR people are the worse interviewers from experience.
Here's the main tips.
Be early, not too early, about 5-10 minutes. If you're too early you'll start to feel awkward and probably increase your nervousness.
Ensure you dress appropriately for the position you're applying for but dress smartly regardless.
Know the company you're applying for. Learn about their values. Their style of working, etc. Use their website as a means of finding out about them.
Use LinkedIn to find out about the people interviewing you if they're on there.
Have questions prepared to ask them, about work environment, etc. Don't ask about pay, unless they bring it up. Very important.
Have prepared answers ready but don't blurt things out. Listen to the questions carefully. Take a breath, than answer if you can. There's no need to rush. Speak slowly and calmly.
Realise that the person interviewing you is probably not a fan of interviews either so as they evaluate you, you evaluate them.
I agree with not lying, that's never a good idea. More importantly, don't provide negative answers to questions. Even the question, "what is your weakness" should be turned into a positive. It should also be a answer suitable for the position you're applying for.
It's only natural to be nervous. I've done a lot of interviews and I still get a touch nervous doing them.
My final bit of advice is this. It's your first interview for your first full time job. You're going to put a lot of emphasis on how important this is for you and wanting to get this job. That will stress you out more than the actual interview. Just realise that this is one step of many.
Get some good sleep, prepare your things the night before, get there early, learn from the experience regardless what the outcome is.