Think ahead. Know the main messages that you want to get across beforehand and think about the type of questions that will help you share them.
Do your research. Be well informed about the person you are meeting and the organisation they represent. This will flatter them and show you are serious.
Find out what they're after. Ask at the outset what they would most like to get out of your time together. This will help you focus what you say and also give you some kind of control over what happens.
Be enthusiastic - it's hard to resist. The person you are talking with has probably had a fairly dull day. An energetic and keen interviewee is sure to cheer them up.
Tell stories to make your points. Not only are they more memorable but, if you choose them wisely, they'll highlight strengths subtly (you can't tell someone that you are flexible, determined and great at getting results, but you can share a tale that illustrates these traits).
Ask questions. People are generally more engaged when they are talking and being listened to than the other way round. Ideally, your questions will also show off your knowledge and your intellect.
Smile at some stage. It will show you are human and don't take life too seriously.
Treat the other person as an equal. The best and most enjoyable interviews don't feel like interviews but stimulating conversations between two interesting and dynamic people.
If you don't succeed, try again. If for some reason the interview doesn't go well, there is no shame in getting back in touch, explaining that you weren't on form and asking to meet again. You'd be surprised how many senior people started that way.