Be polite. Listen to each question fully before you begin to respond. Never assume that your interviewer has read your CV, but don't treat him or her as though he or she hasn't, either. After the interview, do not forget to send a follow up thank you-email. These are generally better than hand written thank you notes, as they are quicker than snail mail. However, you should be sure that they are well proofread and personal before you send them.