Think of perceptive questions to express that you're curious and have thought about the opportunity.
Try not to oversell who you are.
Think about your responses.
Do not be worried to declare you don't know an answer.
Don't be late. Prepare for delays.
Do not go off topic. Keep your thoughts on the things you are good at.
Analyse typical questions and write down your replies.
Advice for those looking for employment:
"Follow-up, keep records. No matter what searching tactics chosen, follow-up and making sure you keep tabs are crucial for getting that job. Those who don't store this info probably lose useful contacts, likewise plausibility with prospective companies."