I have been sitting on lots of interview panels as the lead lately, we have recruited around 12 people into the team that I manage.
Advice that I can offer:-
Make sure you know the job description - its amazing how many people show up not having a clue.
Research the business who is offering the job, know their work and their clients.
Wear a suit and tie, black shoes.
Be polite.
Have some questions prepped for them - remember you should be checking that this job is suitable for you as well. I find an approach of I'm interviewing them a bit really helps to take the pressure off.
Don't bulls&*t - they will know.
Lastly for now and this should go without saying - be on time!
People who we have interviewed recently who have not got a role include:
Those who didn't show up and didn't tell us they were cancelling
People not smart - who doesn't wear a tie/jacket to a professional interview
People who had no idea what the role is about
People who had no idea what our business does
You get the picture!
Good Luck