Explain the goals of your career and the reasons you like the opportunity.
Be sincere, upbeat, focused, self-assured, frank and succint.
Put on a clean suit. Wear it sharp and clean.
Say thank you to your interviewer at the end and after by email or send a 'thank you' card by post.
Don't be late. Plan for delays.
Make a Google Alert on the firm to know latest developments.
Take a seat, be calm, take some time to set yourself ahead of entering reception.
Suggestions for those looking for employment:
"Research. Before you apply (but especially before you go to the interview), be sure to discover as much as you can about your prospective employer. Be sure to understand exactly what it is that they do, their market, their competition and values. Remain current on any issues or developments in the field. Read trade journals or professional publications and read the newspaper."