Be honest, understand what you're looking for from the company and make sure you get this across. Be yourself and don't try to second guess the interviewer.
Prepare. Research the company and have questions prepared and ask them.
Be on time!
Firstly, take a breath. Whatever happens next, you will be fine. The person or people doing the interview want to have a fantastic workforce and they want you to do well. They are looking for someone who wants the job and will do it to the best of their abilities. Be that person!
Read up about the company. Think of questions you may be asked & your answers. Think of questions you want to ask them. Know where you are going, how to get there & how long it will take. Dress appropriately!
Think of times when you have shown leadership and other characteristics.
If needed, ask for time to consider your answer.