[Redbob]

It's unlikely you'll be doing salary negotiations in a first interview.

Like others have said:
Dress professionally;
Get an "adult's" haircut;
Get there early - arriving late is the kiss of death!
Be prepared to tell them where you see yourself working in 5 years; and if it's someplace else - lie!
And relax - it's only an interview.

Good luck!

[DouglasKC]

Be prepared to tell them where you see yourself working in 5 years; and if it's someplace else - lie!

To add to this...be careful with this question. If one of the people interviewing is your future boss, they might feel threatened if one of your career goals is to become a manager in your field.

I'm a little older than you (40), but I've always found the best answer to be "I really love the kind of work(field) I'm in right now and frankly would be glad to work in it in any capacity."