Your interview is the culmination of several efforts. If you've gotten this far then this next step is the most important step you can take. You've made the contact, you've made them interested in you, you've peaked their curiosity on how you can help them move forward, now it's time to close the deal.
Things to do:
Have your elevator story
Dress appropriate for the job you are applying for.
Make eye contact
Use mirroring and matching
Empathic listening
Figure out what questions you want to ask in advance, memorize them
Don't over answer the question, don't share too much
Preparation
Do your research
Practice if even to the mirror
Practice out loud
Record your practice sessions
Things to remember:
You need the practice
Interview for as many jobs as you can.
This will help you define yourself in the marketplace
It is the beginning of your networking process
It may create opportunities you hadn't considered.