Do not be fearful to declare you don't know an answer.
Don't worry by thinking of pessemistic happenings.
Eat an energising meal beforehand - but no smelly meals!
Be sincere, upbeat, sure of yourself, frank and to the point.
Do not go off topic. Keep your thoughts on the things you are good at.
Check your latest twitter and linkedin messages are interview safe.
Suggestions for those looking for employment:
"Before you apply, make sure you discover information about your prospective employer. Understand exactly what they do, their sector, their competition and principles. Stay on top of any issues or news in the sector."