You have such enthusiam I can't imagine why they wouldn't hire you. You'd be an asset to them.
1. Know where you're going and who you'll be meeting with.
2. Confidence : remember a company that calls you for an interview believes you are capable of doing the job.
3. Show excitement about the tasks you'll be ask to do.
4. If possible talk with someone who already has the position and learn what's expected of them.
5. Know as much as you can about the company. Interviewers love it when you've taken the time to educate yourself about their company.
6. Practice your interview. Whether in front of a mirror or with a friend this will do wonders for helping you remain calm .
7. Never, never go negative. When asked about any former boss, teacher, or aquaintance always speak positively.
If you can get a copy of the Everything Job Interview Book, I highly reccomend it. Check the local library if they don't have it. Buy it, you'll be glad you did.