Hi Julie,
Well just like any interview you may have, you need to dress out neatly, formal is highly preferred. Don't put a lot of make-up. If you are wearing a skirt, make sure its not too short .
During the interview, keep smiling and try to give brief answers; not too short - not too long.
Try to avoid talking about the political situation in Lebanon or religion. People tend to talk about these topics here very often, but it gets them nowhere.
Im sure you will be asked why you want to come to Lebanon. If I were you, I would say Beirut is the center of the Middle East where many cultures and people from different backgrounds meet here. Its an open society. The country is amazing and there are a lot to see in Lebanon. Apart from the traffic, Beirut is the place to be!
Last but not least, I would you say something in Arabic. Thank you means "Shokran". Do you use it when you're finishing up.
Good Luck
Ali