My first professional interview is tommorow. How should I prepare for it?

I got a interview tommorow for this Human Resource marketing company. It is for a "management trainee" position. I'm not sure if I'm going to be trained has a manager or if I go out and train potential managers.

How do I prepare for the interview?
They want me to bring 2 copies of my resume and dress professional. I want to give it my best shot.

Your insight please!

A management trainee is being trained as a manager, not someone who trains managers (that would be a management trainer). You need to do several things. First of all, definitely have nice copies of your resume available and dress professionally, and make sure you show up on time. Secondly, you need to do some research on the company, so that you can show an interest in what they do. Look up their website and make sure you know what is important to them. Google them so that you can see if they have done anything interesting as a company lately. If you know who is going to be interviewing you, you can Google them too, to see if they have done something like win any awards recently. Also, you should prepare a few questions about the company, in case they give you time to ask them. Not questions about salary or vacations or other things that will sound like, "What do I get out of this job?", but things like, "What is the typical career path for a trainee?" "What would be your idea of the perfect graduate of your training program? What would you hope a new manager would be able to contribute to your company?" This shows that you want to do well, and that you care about what the company wants, rather than just looking at what you can get from the job. Remember that they are looking at you as someone who can contribute to their company. They are not a charity trying to help the neediest person, but a company looking to improve their bottom line by hiring you.

1. Bring 2 copies of your resume
2. Dress professional

To be more specific - make sure your resumes are in clean large envelopes. Don't fold them. Your resume should be done professionally also, everything spelled correctly. It counts.
Assuming you are qualified for the job - dress like you are going to church. No jeans, no raggy clothes. No face jewelry, hide the tattoos (you are dealing with old folks here), wear tiny earrings if you are a girl, NO earrings if you are a guy (I know, I know, you like the look, but remember who you are dealing with), CLEAN and cut short fingernails.
If you are a guy - a clean sharp shirt with a tie that is conservative. If you expect to be in business you gotta look the part. And girls - no low cut ANYTHING. Do not show boobs, do not show a lot of leg. Wear shoes that have closed toes and heels and nylons. No jewelry except a watch, one ring or rings if married. Clean, well groomed. No perfume at all.
But the best thing you can wear...is a smile and a "can do" attitude. If they ask if you can speak spanish and you don't - say "I'll learn." Be willing to go the extra mile -
And GOOD LUCK! Go to bed at a decent time, have a good breakfast tomorrow, look in the mirror and say - I AM GOOD.